/**

  * $Id$

  *

  * Manage the internal vertex/polygon buffers and scene data structure.

  * Where possible this uses VBOs for the vertex + index data.

  *

  * Copyright (c) 2005 Nathan Keynes.

  *

  * This program is free software; you can redistribute it and/or modify

  * it under the terms of the GNU General Public License as published by

  * the Free Software Foundation; either version 2 of the License, or

  * (at your option) any later version.

  *

  * This program is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  * GNU General Public License for more details.

  */

 #include <assert.h>

 #include <string.h>

 #include <math.h>

 #include "lxdream.h"

 #include "display.h"

 #include "pvr2/pvr2.h"

 #include "pvr2/pvr2mmio.h"

 #include "pvr2/glutil.h"

 #include "pvr2/scene.h"

 #define U8TOFLOAT(n)  (((float)((n)+1))/256.0)

 static void unpack_bgra(uint32_t bgra, float *rgba)

 {

     rgba[0] = ((float)(((bgra&0x00FF0000)>>16) + 1)) / 256.0;

     rgba[1] = ((float)(((bgra&0x0000FF00)>>8) + 1)) / 256.0;

     rgba[2] = ((float)((bgra&0x000000FF) + 1)) / 256.0;

     rgba[3] = ((float)(((bgra&0xFF000000)>>24) + 1)) / 256.0;

 }

 static inline uint32_t bgra_to_rgba(uint32_t bgra)

 {

     return (bgra&0xFF00FF00) | ((bgra&0x00FF0000)>>16) | ((bgra&0x000000FF)<<16);

 }

 /**

  * Convert a half-float (16-bit) FP number to a regular 32-bit float.

  * Source is 1-bit sign, 5-bit exponent, 10-bit mantissa.

  * TODO: Check the correctness of this.

  */

 static float halftofloat( uint16_t half )

 {

     union {

         float f;

         uint32_t i;

     } temp;

     temp.i = ((uint32_t)half)<<16;

     return temp.f;

 }

 static float parse_fog_density( uint32_t value )

 {

     union {

         uint32_t i;

         float f;

     } u;

     u.i = (((value+127)&0xFF)<<23)|((value & 0xFF00)<<7);

     return u.f;

 }

 struct pvr2_scene_struct pvr2_scene;

 static gboolean vbo_init = FALSE;

 static float scene_shadow_intensity = 0.0;

 #ifdef ENABLE_VERTEX_BUFFER

 static gboolean vbo_supported = FALSE;

 #endif

 /**

  * Test for VBO support, and allocate all the system memory needed for the

  * temporary structures. GL context must have been initialized before this

  * point.

  */

 void pvr2_scene_init()

 {

     if( !vbo_init ) {

 #ifdef ENABLE_VERTEX_BUFFER

         if( isGLVertexBufferSupported() ) {

             vbo_supported = TRUE;

             pvr2_scene.vbo_id = 1;

         }

 #endif

         pvr2_scene.vertex_array = NULL;

         pvr2_scene.vertex_array_size = 0;

         pvr2_scene.poly_array = g_malloc( MAX_POLY_BUFFER_SIZE );

         pvr2_scene.buf_to_poly_map = g_malloc0( BUF_POLY_MAP_SIZE );

         vbo_init = TRUE;

     }

 }

 /**

  * Clear the scene data structures in preparation for fresh data

  */

 void pvr2_scene_reset()

 {

     pvr2_scene.poly_count = 0;

     pvr2_scene.vertex_count = 0;

     memset( pvr2_scene.buf_to_poly_map, 0, BUF_POLY_MAP_SIZE );

 }

 void pvr2_scene_shutdown()

 {

 #ifdef ENABLE_VERTEX_BUFFER

     if( vbo_supported ) {

         glBindBufferARB( GL_ARRAY_BUFFER_ARB, 0 );

         glDeleteBuffersARB( 1, &pvr2_scene.vbo_id );

         pvr2_scene.vbo_id = 0;

     } else {

 #endif

         g_free( pvr2_scene.vertex_array );

         pvr2_scene.vertex_array = NULL;

 #ifdef ENABLE_VERTEX_BUFFER

     }

 #endif

     g_free( pvr2_scene.poly_array );

     pvr2_scene.poly_array = NULL;

     g_free( pvr2_scene.buf_to_poly_map );

     pvr2_scene.buf_to_poly_map = NULL;

     vbo_init = FALSE;

 }

 void *vertex_buffer_map()

 {

     // Allow 8 vertexes for the background (4+4)

     uint32_t size = (pvr2_scene.vertex_count + 8) * sizeof(struct vertex_struct);

 #ifdef ENABLE_VERTEX_BUFFER

     if( vbo_supported ) {

         glGetError();

         glBindBufferARB( GL_ARRAY_BUFFER_ARB, pvr2_scene.vbo_id );

         if( size > pvr2_scene.vertex_array_size ) {

             glBufferDataARB( GL_ARRAY_BUFFER_ARB, size, NULL, GL_DYNAMIC_DRAW_ARB );

             int status = glGetError();

             if( status != 0 ) {

                 fprintf( stderr, "Error %08X allocating vertex buffer\n", status );

                 abort();

             }

             pvr2_scene.vertex_array_size = size;

         }

         pvr2_scene.vertex_array = glMapBufferARB( GL_ARRAY_BUFFER_ARB, GL_WRITE_ONLY_ARB );

         assert(pvr2_scene.vertex_array != NULL );

     } else {

 #endif

         if( size > pvr2_scene.vertex_array_size ) {

             pvr2_scene.vertex_array = g_realloc( pvr2_scene.vertex_array, size );

         }

 #ifdef ENABLE_VERTEX_BUFFER

     }

 #endif

     return pvr2_scene.vertex_array;

 }

 gboolean vertex_buffer_unmap()

 {

 #ifdef ENABLE_VERTEX_BUFFER

     if( vbo_supported ) {

         pvr2_scene.vertex_array = NULL;

         return glUnmapBufferARB( GL_ARRAY_BUFFER_ARB );

     } else {

         return TRUE;

     }

 #else

     return TRUE;

 #endif

 }

 static struct polygon_struct *scene_add_polygon( pvraddr_t poly_idx, int vertex_count,

                                                  shadow_mode_t is_modified )

 {

     int vert_mul = is_modified != SHADOW_NONE ? 2 : 1;

     if( pvr2_scene.buf_to_poly_map[poly_idx] != NULL ) {

         if( vertex_count > pvr2_scene.buf_to_poly_map[poly_idx]->vertex_count ) {

             pvr2_scene.vertex_count += (vertex_count - pvr2_scene.buf_to_poly_map[poly_idx]->vertex_count) * vert_mul;

             pvr2_scene.buf_to_poly_map[poly_idx]->vertex_count = vertex_count;

         }

         return pvr2_scene.buf_to_poly_map[poly_idx];

     } else {

         struct polygon_struct *poly = &pvr2_scene.poly_array[pvr2_scene.poly_count++];

         poly->context = &pvr2_scene.pvr2_pbuf[poly_idx];

         poly->vertex_count = vertex_count;

         poly->vertex_index = -1;

         poly->mod_vertex_index = -1;

         poly->next = NULL;

         pvr2_scene.buf_to_poly_map[poly_idx] = poly;

         pvr2_scene.vertex_count += (vertex_count * vert_mul);

         return poly;

     }

 }

 /**

  * Decode a single PVR2 renderable vertex (opaque/trans/punch-out, but not shadow

  * volume)

  * @param vert Pointer to output vertex structure

  * @param poly1 First word of polygon context (needed to understand vertex)

  * @param poly2 Second word of polygon context

  * @param pvr2_data Pointer to raw pvr2 vertex data (in VRAM)

  * @param modify_offset Offset in 32-bit words to the tex/color data. 0 for

  *        the normal vertex, half the vertex length for the modified vertex.

  */

 static void pvr2_decode_render_vertex( struct vertex_struct *vert, uint32_t poly1,

                                        uint32_t poly2, uint32_t *pvr2_data,

                                        int modify_offset )

 {

     gboolean force_alpha = !POLY2_ALPHA_ENABLE(poly2);

     union pvr2_data_type {

         uint32_t *ival;

         float *fval;

     } data;

     data.ival = pvr2_data;

     vert->x = *data.fval++;

     vert->y = *data.fval++;

     float z = *data.fval++;

     if( !isfinite(z) ) {

         z = 0;

     } else if( z != 0 ) {

         z = 1/z;

     }

     if( z > pvr2_scene.bounds[5] ) {

         pvr2_scene.bounds[5] = z;

     } else if( z < pvr2_scene.bounds[4] && z != 0 ) {

         pvr2_scene.bounds[4] = z;

     }

     vert->z = z;

     data.ival += modify_offset;

     if( POLY1_TEXTURED(poly1) ) {

         if( POLY1_UV16(poly1) ) {

             vert->u = halftofloat( *data.ival>>16 );

             vert->v = halftofloat( *data.ival );

             data.ival++;

         } else {

             vert->u = *data.fval++;

             vert->v = *data.fval++;

         }

         if( POLY2_TEX_BLEND(poly2) == 1 ) {

             force_alpha = TRUE;

         }

     }

     unpack_bgra(*data.ival++, vert->rgba);

     if( POLY1_SPECULAR(poly1) ) {

         unpack_bgra(*data.ival++, vert->offset_rgba);

     } else {

         vert->offset_rgba[0] = 0.0;

         vert->offset_rgba[1] = 0.0;

         vert->offset_rgba[2] = 0.0;

         vert->offset_rgba[3] = 0.0;

     }

     if( force_alpha ) {

         vert->rgba[3] = 1.0;

     }

 }

 /**

  * Compute texture, colour, and z values for 1 or more result points by interpolating from

  * a set of 3 input points. The result point(s) must define their x,y.

  */

 static void scene_compute_vertexes( struct vertex_struct *result,

                                     int result_count,

                                     struct vertex_struct *input,

                                     gboolean is_solid_shaded )

 {

     int i,j;

     float sx = input[2].x - input[1].x;

     float sy = input[2].y - input[1].y;

     float tx = input[0].x - input[1].x;

     float ty = input[0].y - input[1].y;

     float detxy = ((sy) * (tx)) - ((ty) * (sx));

     if( detxy == 0 ) {

         // If the input points fall on a line, they don't define a usable

         // polygon - the PVR2 takes the last input point as the result in

         // this case.

         for( i=0; i<result_count; i++ ) {

             float x = result[i].x;

             float y = result[i].y;

             memcpy( &result[i], &input[2], sizeof(struct vertex_struct) );

             result[i].x = x;

             result[i].y = y;

         }

         return;

     }

     float sz = input[2].z - input[1].z;

     float tz = input[0].z - input[1].z;

     float su = input[2].u - input[1].u;

     float tu = input[0].u - input[1].u;

     float sv = input[2].v - input[1].v;

     float tv = input[0].v - input[1].v;

     for( i=0; i<result_count; i++ ) {

         float t = ((result[i].x - input[1].x) * sy -

                 (result[i].y - input[1].y) * sx) / detxy;

         float s = ((result[i].y - input[1].y) * tx -

                 (result[i].x - input[1].x) * ty) / detxy;

         float rz = input[1].z + (t*tz) + (s*sz);

         if( rz > pvr2_scene.bounds[5] ) {

             pvr2_scene.bounds[5] = rz;

         } else if( rz < pvr2_scene.bounds[4] ) {

             pvr2_scene.bounds[4] = rz;

         }

         result[i].z = rz;

         result[i].u = input[1].u + (t*tu) + (s*su);

         result[i].v = input[1].v + (t*tv) + (s*sv);

         if( is_solid_shaded ) {

             memcpy( result->rgba, input[2].rgba, sizeof(result->rgba) );

             memcpy( result->offset_rgba, input[2].offset_rgba, sizeof(result->offset_rgba) );

         } else {

             float *rgba0 = input[0].rgba;

             float *rgba1 = input[1].rgba;

             float *rgba2 = input[2].rgba;

             float *rgba3 = result[i].rgba;

             for( j=0; j<8; j++ ) {

                 float tc = *rgba0++ - *rgba1;

                 float sc = *rgba2++ - *rgba1;

                 float rc = *rgba1++ + (t*tc) + (s*sc);

                 *rgba3++ = rc;

             }

         }

     }

 }

 static float scene_compute_lut_fog_vertex( float z, float fog_density, float fog_table[][2] )

 {

     union {

         uint32_t i;

         float f;

     } v;

     v.f = z * fog_density;

     if( v.f < 1.0 ) v.f = 1.0;

     else if( v.f > 255.9999 ) v.f = 255.9999;

     uint32_t index = ((v.i >> 18) & 0x0F)|((v.i>>19)&0x70);

     return fog_table[index][0];

 }

 /**

  * Compute the fog coefficients for all polygons using lookup-table fog. It's 

  * a little more convenient to do this as a separate pass, since we don't have

  * to worry about computed vertexes.

  */

 static void scene_compute_lut_fog( )

 {

     int i,j;

     float fog_density = parse_fog_density(MMIO_READ( PVR2, RENDER_FOGCOEFF ));

     float fog_table[128][2];

     /* Parse fog table out into floating-point format */

     for( i=0; i<128; i++ ) {

         uint32_t ent = MMIO_READ( PVR2, RENDER_FOGTABLE + (i<<2) );

         fog_table[i][0] = ((float)(((ent&0x0000FF00)>>8) + 1)) / 256.0;

         fog_table[i][1] = ((float)((ent&0x000000FF) + 1)) / 256.0;

     }

     for( i=0; i<pvr2_scene.poly_count; i++ ) {

         int mode = POLY2_FOG_MODE(pvr2_scene.poly_array[i].context[1]);

         if( mode == PVR2_POLY_FOG_LOOKUP ) {

             uint32_t index = pvr2_scene.poly_array[i].vertex_index;

             for( j=0; j<=pvr2_scene.poly_array[i].vertex_count; j++ ) {

                 pvr2_scene.vertex_array[index+j].offset_rgba[3] = 

                     scene_compute_lut_fog_vertex( pvr2_scene.vertex_array[index+j].z, fog_density, fog_table );

             }

         } else if( mode == PVR2_POLY_FOG_LOOKUP2 ) {

             uint32_t index = pvr2_scene.poly_array[i].vertex_index;

             for( j=0; j<=pvr2_scene.poly_array[i].vertex_count; j++ ) {

                 pvr2_scene.vertex_array[index+j].rgba[0] = pvr2_scene.fog_lut_colour[0];

                 pvr2_scene.vertex_array[index+j].rgba[1] = pvr2_scene.fog_lut_colour[1];

                 pvr2_scene.vertex_array[index+j].rgba[2] = pvr2_scene.fog_lut_colour[2];

                 pvr2_scene.vertex_array[index+j].rgba[3] = 

                     scene_compute_lut_fog_vertex( pvr2_scene.vertex_array[index+j].z, fog_density, fog_table );

             }

         }

     }    

 }

 static void scene_add_cheap_shadow_vertexes( struct vertex_struct *src, struct vertex_struct *dest, int count )

 {

     unsigned int i, j;

     for( i=0; i<count; i++ ) {

         dest->x = src->x;

         dest->y = src->y;

         dest->z = src->z;

         dest->u = src->u;

         dest->v = src->v;

         dest->rgba[0] = src->rgba[0] * scene_shadow_intensity;

         dest->rgba[1] = src->rgba[1] * scene_shadow_intensity;

         dest->rgba[2] = src->rgba[2] * scene_shadow_intensity;

         dest->rgba[3] = src->rgba[3] * scene_shadow_intensity;

         dest->offset_rgba[0] = src->offset_rgba[0] * scene_shadow_intensity;

         dest->offset_rgba[1] = src->offset_rgba[1] * scene_shadow_intensity;

         dest->offset_rgba[2] = src->offset_rgba[2] * scene_shadow_intensity;

         dest->offset_rgba[3] = src->offset_rgba[3];

         dest++;

         src++;

     }

 }

 static void scene_add_vertexes( pvraddr_t poly_idx, int vertex_length,

                                 shadow_mode_t is_modified )

 {

     struct polygon_struct *poly = pvr2_scene.buf_to_poly_map[poly_idx];

     uint32_t *ptr = &pvr2_scene.pvr2_pbuf[poly_idx];

     uint32_t *context = ptr;

     unsigned int i;

     if( poly->vertex_index == -1 ) {

         ptr += (is_modified == SHADOW_FULL ? 5 : 3 );

         poly->vertex_index = pvr2_scene.vertex_index;

         assert( poly != NULL );

         assert( pvr2_scene.vertex_index + poly->vertex_count <= pvr2_scene.vertex_count );

         for( i=0; i<poly->vertex_count; i++ ) {

             pvr2_decode_render_vertex( &pvr2_scene.vertex_array[pvr2_scene.vertex_index++], context[0], context[1], ptr, 0 );

             ptr += vertex_length;

         }

         if( is_modified ) {

             assert( pvr2_scene.vertex_index + poly->vertex_count <= pvr2_scene.vertex_count );

             poly->mod_vertex_index = pvr2_scene.vertex_index;

             if( is_modified == SHADOW_FULL ) {

                 int mod_offset = (vertex_length - 3)>>1;

                 ptr = &pvr2_scene.pvr2_pbuf[poly_idx] + 5;

                 for( i=0; i<poly->vertex_count; i++ ) {

                     pvr2_decode_render_vertex( &pvr2_scene.vertex_array[pvr2_scene.vertex_index++], context[0], context[3], ptr, mod_offset );

                     ptr += vertex_length;

                 }

             } else {

                 scene_add_cheap_shadow_vertexes( &pvr2_scene.vertex_array[poly->vertex_index], 

                         &pvr2_scene.vertex_array[poly->mod_vertex_index], poly->vertex_count );

                 pvr2_scene.vertex_index += poly->vertex_count;

             }

         }

     }

 }

 static void scene_add_quad_vertexes( pvraddr_t poly_idx, int vertex_length,

                                      shadow_mode_t is_modified )

 {

     struct polygon_struct *poly = pvr2_scene.buf_to_poly_map[poly_idx];

     uint32_t *ptr = &pvr2_scene.pvr2_pbuf[poly_idx];

     uint32_t *context = ptr;

     unsigned int i;

     if( poly->vertex_index == -1 ) {

         // Construct it locally and copy to the vertex buffer, as the VBO is

         // allowed to be horribly slow for reads (ie it could be direct-mapped

         // vram).

         struct vertex_struct quad[4];

         assert( poly != NULL );

         assert( pvr2_scene.vertex_index + poly->vertex_count <= pvr2_scene.vertex_count );

         ptr += (is_modified == SHADOW_FULL ? 5 : 3 );

         poly->vertex_index = pvr2_scene.vertex_index;

         for( i=0; i<4; i++ ) {

             pvr2_decode_render_vertex( &quad[i], context[0], context[1], ptr, 0 );

             ptr += vertex_length;

         }

         scene_compute_vertexes( &quad[3], 1, &quad[0], !POLY1_GOURAUD_SHADED(context[0]) );

         // Swap last two vertexes (quad arrangement => tri strip arrangement)

         memcpy( &pvr2_scene.vertex_array[pvr2_scene.vertex_index], quad, sizeof(struct vertex_struct)*2 );

         memcpy( &pvr2_scene.vertex_array[pvr2_scene.vertex_index+2], &quad[3], sizeof(struct vertex_struct) );

         memcpy( &pvr2_scene.vertex_array[pvr2_scene.vertex_index+3], &quad[2], sizeof(struct vertex_struct) );

         pvr2_scene.vertex_index += 4;

         if( is_modified ) {

             assert( pvr2_scene.vertex_index + poly->vertex_count <= pvr2_scene.vertex_count );

             poly->mod_vertex_index = pvr2_scene.vertex_index;

             if( is_modified == SHADOW_FULL ) {

                 int mod_offset = (vertex_length - 3)>>1;

                 ptr = &pvr2_scene.pvr2_pbuf[poly_idx] + 5;

                 for( i=0; i<4; i++ ) {

                     pvr2_decode_render_vertex( &quad[4], context[0], context[3], ptr, mod_offset );

                     ptr += vertex_length;

                 }

                 scene_compute_vertexes( &quad[3], 1, &quad[0], !POLY1_GOURAUD_SHADED(context[0]) );

                 memcpy( &pvr2_scene.vertex_array[pvr2_scene.vertex_index], quad, sizeof(struct vertex_struct)*2 );

                 memcpy( &pvr2_scene.vertex_array[pvr2_scene.vertex_index+2], &quad[3], sizeof(struct vertex_struct) );

                 memcpy( &pvr2_scene.vertex_array[pvr2_scene.vertex_index+3], &quad[2], sizeof(struct vertex_struct) );

             } else {

                 scene_add_cheap_shadow_vertexes( &pvr2_scene.vertex_array[poly->vertex_index], 

                         &pvr2_scene.vertex_array[poly->mod_vertex_index], poly->vertex_count );

                 pvr2_scene.vertex_index += poly->vertex_count;

             }

             pvr2_scene.vertex_index += 4;

         }

     }

 }

 static void scene_extract_polygons( pvraddr_t tile_entry )

 {

     uint32_t *tile_list = (uint32_t *)(pvr2_main_ram+tile_entry);

     do {

         uint32_t entry = *tile_list++;

         if( entry >> 28 == 0x0F ) {

             break;

         } else if( entry >> 28 == 0x0E ) {

             tile_list = (uint32_t *)(pvr2_main_ram + (entry&0x007FFFFF));

         } else {

             pvraddr_t polyaddr = entry&0x000FFFFF;

             shadow_mode_t is_modified = (entry & 0x01000000) ? pvr2_scene.shadow_mode : SHADOW_NONE;

             int vertex_length = (entry >> 21) & 0x07;

             int context_length = 3;

             if( is_modified == SHADOW_FULL ) {

                 context_length = 5;

                 vertex_length <<= 1 ;

             }

             vertex_length += 3;

             if( (entry & 0xE0000000) == 0x80000000 ) {

                 /* Triangle(s) */

                 int strip_count = ((entry >> 25) & 0x0F)+1;

                 int polygon_length = 3 * vertex_length + context_length;

                 int i;

                 struct polygon_struct *last_poly = NULL;

                 for( i=0; i<strip_count; i++ ) {

                     struct polygon_struct *poly = scene_add_polygon( polyaddr, 3, is_modified );

                     polyaddr += polygon_length;

                     if( last_poly != NULL && last_poly->next == NULL ) {

                         last_poly->next = poly;

                     }

                     last_poly = poly;

                 }

             } else if( (entry & 0xE0000000) == 0xA0000000 ) {

                 /* Sprite(s) */

                 int strip_count = ((entry >> 25) & 0x0F)+1;

                 int polygon_length = 4 * vertex_length + context_length;

                 int i;

                 struct polygon_struct *last_poly = NULL;

                 for( i=0; i<strip_count; i++ ) {

                     struct polygon_struct *poly = scene_add_polygon( polyaddr, 4, is_modified );

                     polyaddr += polygon_length;

                     if( last_poly != NULL && last_poly->next == NULL ) {

                         last_poly->next = poly;

                     }

                     last_poly = poly;

                 }

             } else {

                 /* Polygon */

                 int i, last = -1;

                 for( i=5; i>=0; i-- ) {

                     if( entry & (0x40000000>>i) ) {

                         last = i;

                         break;

                     }

                 }

                 if( last != -1 ) {

                     scene_add_polygon( polyaddr, last+3, is_modified );

                 }

             }

         }

     } while( 1 );

 }

 static void scene_extract_vertexes( pvraddr_t tile_entry )

 {

     uint32_t *tile_list = (uint32_t *)(pvr2_main_ram+tile_entry);

     do {

         uint32_t entry = *tile_list++;

         if( entry >> 28 == 0x0F ) {

             break;

         } else if( entry >> 28 == 0x0E ) {

             tile_list = (uint32_t *)(pvr2_main_ram + (entry&0x007FFFFF));

         } else {

             pvraddr_t polyaddr = entry&0x000FFFFF;

             shadow_mode_t is_modified = (entry & 0x01000000) ? pvr2_scene.shadow_mode : SHADOW_NONE;

             int vertex_length = (entry >> 21) & 0x07;

             int context_length = 3;

             if( is_modified == SHADOW_FULL ) {

                 context_length = 5;

                 vertex_length <<=1 ;

             }

             vertex_length += 3;

             if( (entry & 0xE0000000) == 0x80000000 ) {

                 /* Triangle(s) */

                 int strip_count = ((entry >> 25) & 0x0F)+1;

                 int polygon_length = 3 * vertex_length + context_length;

                 int i;

                 for( i=0; i<strip_count; i++ ) {

                     scene_add_vertexes( polyaddr, vertex_length, is_modified );

                     polyaddr += polygon_length;

                 }

             } else if( (entry & 0xE0000000) == 0xA0000000 ) {

                 /* Sprite(s) */

                 int strip_count = ((entry >> 25) & 0x0F)+1;

                 int polygon_length = 4 * vertex_length + context_length;

                 int i;

                 for( i=0; i<strip_count; i++ ) {

                     scene_add_quad_vertexes( polyaddr, vertex_length, is_modified );

                     polyaddr += polygon_length;

                 }

             } else {

                 /* Polygon */

                 int i, last = -1;

                 for( i=5; i>=0; i-- ) {

                     if( entry & (0x40000000>>i) ) {

                         last = i;

                         break;

                     }

                 }

                 if( last != -1 ) {

                     scene_add_vertexes( polyaddr, vertex_length, is_modified );

                 }

             }

         }

     } while( 1 );

 }

 static void scene_extract_background( void )

 {

     uint32_t bgplane = MMIO_READ(PVR2, RENDER_BGPLANE);

     int vertex_length = (bgplane >> 24) & 0x07;

     int context_length = 3, i;

     shadow_mode_t is_modified = (bgplane & 0x08000000) ? pvr2_scene.shadow_mode : SHADOW_NONE;

     struct polygon_struct *poly = &pvr2_scene.poly_array[pvr2_scene.poly_count++];

     uint32_t *context = &pvr2_scene.pvr2_pbuf[(bgplane & 0x00FFFFFF)>>3];

     poly->context = context;

     poly->vertex_count = 4;

     poly->vertex_index = pvr2_scene.vertex_count;

     if( is_modified == SHADOW_FULL ) {

         context_length = 5;

         vertex_length <<= 1;

     }

     if( is_modified != SHADOW_NONE ) {

         poly->mod_vertex_index = pvr2_scene.vertex_count + 4;

         pvr2_scene.vertex_count += 8;

     } else {

         poly->mod_vertex_index = -1;

         pvr2_scene.vertex_count += 4;

     }

     vertex_length += 3;

     context_length += (bgplane & 0x07) * vertex_length;

     poly->next = NULL;

     pvr2_scene.bkgnd_poly = poly;

     struct vertex_struct base_vertexes[3];

     uint32_t *ptr = context + context_length;

     for( i=0; i<3; i++ ) {

         pvr2_decode_render_vertex( &base_vertexes[i], context[0], context[1],

                 ptr, 0 );

         ptr += vertex_length;

     }

     struct vertex_struct *result_vertexes = &pvr2_scene.vertex_array[poly->vertex_index];

     result_vertexes[0].x = result_vertexes[0].y = 0;

     result_vertexes[1].x = result_vertexes[3].x = pvr2_scene.buffer_width;

     result_vertexes[1].y = result_vertexes[2].x = 0;

     result_vertexes[2].y = result_vertexes[3].y  = pvr2_scene.buffer_height;

     scene_compute_vertexes( result_vertexes, 4, base_vertexes, !POLY1_GOURAUD_SHADED(context[0]) );

     if( is_modified == SHADOW_FULL ) {

         int mod_offset = (vertex_length - 3)>>1;

         ptr = context + context_length;

         for( i=0; i<3; i++ ) {

             pvr2_decode_render_vertex( &base_vertexes[i], context[0], context[3],

                     ptr, mod_offset );

             ptr += vertex_length;

         }

         result_vertexes = &pvr2_scene.vertex_array[poly->mod_vertex_index];

         result_vertexes[0].x = result_vertexes[0].y = 0;

         result_vertexes[1].x = result_vertexes[3].x = pvr2_scene.buffer_width;

         result_vertexes[1].y = result_vertexes[2].x = 0;

         result_vertexes[2].y = result_vertexes[3].y  = pvr2_scene.buffer_height;

         scene_compute_vertexes( result_vertexes, 4, base_vertexes, !POLY1_GOURAUD_SHADED(context[0]) );

     } else if( is_modified == SHADOW_CHEAP ) {

         scene_add_cheap_shadow_vertexes( &pvr2_scene.vertex_array[poly->vertex_index], 

                 &pvr2_scene.vertex_array[poly->mod_vertex_index], poly->vertex_count );

         pvr2_scene.vertex_index += poly->vertex_count;

     }

 }

 uint32_t pvr2_scene_buffer_width()

 {

     return pvr2_scene.buffer_width;

 }

 uint32_t pvr2_scene_buffer_height()

 {

     return pvr2_scene.buffer_height;

 }

 /**

  * Extract the current scene into the rendering structures. We run two passes

  * - first pass extracts the polygons into pvr2_scene.poly_array (finding vertex counts),

  * second pass extracts the vertex data into the VBO/vertex array.

  *

  * Difficult to do in single pass as we don't generally know the size of a

  * polygon for certain until we've seen all tiles containing it. It also means we

  * can count the vertexes and allocate the appropriate size VBO.

  *

  * FIXME: accesses into VRAM need to be bounds-checked properly

  */

 void pvr2_scene_read( void )

 {

     pvr2_scene_init();

     pvr2_scene_reset();

     pvr2_scene.bounds[0] = MMIO_READ( PVR2, RENDER_HCLIP ) & 0x03FF;

     pvr2_scene.bounds[1] = ((MMIO_READ( PVR2, RENDER_HCLIP ) >> 16) & 0x03FF) + 1;

     pvr2_scene.bounds[2] = MMIO_READ( PVR2, RENDER_VCLIP ) & 0x03FF;

     pvr2_scene.bounds[3] = ((MMIO_READ( PVR2, RENDER_VCLIP ) >> 16) & 0x03FF) + 1;

     pvr2_scene.bounds[4] = pvr2_scene.bounds[5] = MMIO_READF( PVR2, RENDER_FARCLIP );

     uint32_t scaler = MMIO_READ( PVR2, RENDER_SCALER );

     if( scaler & SCALER_HSCALE ) {

     	/* If the horizontal scaler is in use, we're (in principle) supposed to

     	 * divide everything by 2. However in the interests of display quality,

     	 * instead we want to render to the unscaled resolution and downsample

     	 * only if/when required.

     	 */

     	pvr2_scene.bounds[1] *= 2;

     }

     uint32_t fog_col = MMIO_READ( PVR2, RENDER_FOGTBLCOL );

     unpack_bgra( fog_col, pvr2_scene.fog_lut_colour );

     fog_col = MMIO_READ( PVR2, RENDER_FOGVRTCOL );

     unpack_bgra( fog_col, pvr2_scene.fog_vert_colour );

     uint32_t *tilebuffer = (uint32_t *)(pvr2_main_ram + MMIO_READ( PVR2, RENDER_TILEBASE ));

     uint32_t *segment = tilebuffer;

     uint32_t shadow = MMIO_READ(PVR2,RENDER_SHADOW);

     pvr2_scene.segment_list = (struct tile_segment *)tilebuffer;

     pvr2_scene.pvr2_pbuf = (uint32_t *)(pvr2_main_ram + MMIO_READ(PVR2,RENDER_POLYBASE));

     pvr2_scene.shadow_mode = shadow & 0x100 ? SHADOW_CHEAP : SHADOW_FULL;

     scene_shadow_intensity = U8TOFLOAT(shadow&0xFF);

     int max_tile_x = 0;

     int max_tile_y = 0;

     int obj_config = MMIO_READ( PVR2, RENDER_OBJCFG );

     int isp_config = MMIO_READ( PVR2, RENDER_ISPCFG );

     if( (obj_config & 0x00200000) == 0 ) {

         if( isp_config & 1 ) {

             pvr2_scene.sort_mode = SORT_NEVER;

         } else {

             pvr2_scene.sort_mode = SORT_ALWAYS;

         }

     } else {

         pvr2_scene.sort_mode = SORT_TILEFLAG;

     }

     // Pass 1: Extract polygon list

     uint32_t control;

     int i;

     do {

         control = *segment++;

         int tile_x = SEGMENT_X(control);

         int tile_y = SEGMENT_Y(control);

         if( tile_x > max_tile_x ) {

             max_tile_x = tile_x;

         }

         if( tile_y > max_tile_y ) {

             max_tile_y = tile_y;

         }

         for( i=0; i<5; i++ ) {

             if( (*segment & NO_POINTER) == 0 ) {

                 scene_extract_polygons( *segment );

             }

             segment++;

         }

     } while( (control & SEGMENT_END) == 0 );

     pvr2_scene.buffer_width = (max_tile_x+1)<<5;

     pvr2_scene.buffer_height = (max_tile_y+1)<<5;

     // Pass 2: Extract vertex data

     vertex_buffer_map();

     pvr2_scene.vertex_index = 0;

     segment = tilebuffer;

     do {

         control = *segment++;

         for( i=0; i<5; i++ ) {

             if( (*segment & NO_POINTER) == 0 ) {

                 scene_extract_vertexes( *segment );

             }

             segment++;

         }

     } while( (control & SEGMENT_END) == 0 );

     scene_extract_background();

     scene_compute_lut_fog();

     vertex_buffer_unmap();

 }

 /**

  * Dump the current scene to file in a (mostly) human readable form

  */

 void pvr2_scene_dump( FILE *f )

 {

     int i,j;

     fprintf( f, "Polygons: %d\n", pvr2_scene.poly_count );

     for( i=0; i<pvr2_scene.poly_count; i++ ) {

         struct polygon_struct *poly = &pvr2_scene.poly_array[i];

         fprintf( f, "  %08X ", ((unsigned char *)poly->context) - pvr2_main_ram );

         switch( poly->vertex_count ) {

         case 3: fprintf( f, "Tri     " ); break;

         case 4: fprintf( f, "Quad    " ); break;

         default: fprintf( f,"%d-Strip ", poly->vertex_count-2 ); break;

         }

         fprintf( f, "%08X %08X %08X ", poly->context[0], poly->context[1], poly->context[2] );

         if( poly->mod_vertex_index != -1 ) {

             fprintf( f, "%08X %08X\n", poly->context[3], poly->context[5] );

         } else {

             fprintf( f, "\n" );

         }

         for( j=0; j<poly->vertex_count; j++ ) {

             struct vertex_struct *v = &pvr2_scene.vertex_array[poly->vertex_index+j];

             fprintf( f, "    %.5f %.5f %.5f, (%.5f,%.5f)  %.5f,%.5f,%.5f,%.5f  %.5f %.5f %.5f %.5f\n", v->x, v->y, v->z, v->u, v->v,

                      v->rgba[0], v->rgba[1], v->rgba[2], v->rgba[3],

                      v->offset_rgba[0], v->offset_rgba[1], v->offset_rgba[2], v->offset_rgba[3] );

         }

         if( poly->mod_vertex_index != -1 ) {

             fprintf( f, "  ---\n" );

             for( j=0; j<poly->vertex_count; j++ ) {

                 struct vertex_struct *v = &pvr2_scene.vertex_array[poly->mod_vertex_index+j];

                 fprintf( f, "    %.5f %.5f %.5f, (%.5f,%.5f)  %.5f,%.5f,%.5f,%.5f  %.5f %.5f %.5f %.5f\n", v->x, v->y, v->z, v->u, v->v,

                          v->rgba[0], v->rgba[1], v->rgba[2], v->rgba[3],

                          v->offset_rgba[0], v->offset_rgba[1], v->offset_rgba[2], v->offset_rgba[3] );

             }

         }

     }

 }