csrDraw.h

   1 typedef struct csr_frag csr_frag;
   2
   3 struct csr_frag
   4 {
   5         u32 id; // Triangle index
   6         float qa, qb;   // Quantities
   7
   8         float depth;    // 'depth testing'
   9 };
  10
  11 void clear_depth( csr_frag fragments[], u32 x, u32 y )
  12 {
  13         for( u32 i = 0; i < x*y; i ++ )
  14         {
  15                 fragments[ i ].depth = INFINITY;
  16         }
  17 }
  18
  19 void simple_raster( csr_frag fragments[], u32 x, u32 y, v4f cam_bounds, vmf_vert tri[3], int id )
  20 {
  21         // Very simplified tracing algorithm
  22
  23         v2f bmin = { 0.f, 0.f };
  24         v2f bmax = { x, y };
  25
  26         v2_minv( tri[0].co, tri[1].co, bmin );
  27         v2_minv( tri[2].co, bmin, bmin );
  28
  29         v2_maxv( tri[0].co, tri[1].co, bmax );
  30         v2_maxv( tri[2].co, bmax, bmax );
  31
  32         float range_x = (cam_bounds[2]-cam_bounds[0])/(float)x;
  33         float range_y = (cam_bounds[3]-cam_bounds[1])/(float)y;
  34
  35         int start_x = csr_max( 0, floorf( (bmin[0]-cam_bounds[0])/range_x));
  36         int end_x =   csr_min( x, floorf( (bmax[0]-cam_bounds[0])/range_x ));
  37         int start_y = csr_max( 0, ceilf( (bmin[1]-cam_bounds[1])/range_y ));
  38         int end_y =   csr_min( y, ceilf( (bmax[1]-cam_bounds[1])/range_y ));
  39
  40         v3f trace_dir = { 0.f, 0.f, -1.f };
  41         v3f trace_origin = { 0.f, 0.f, 16385.f };
  42
  43         for( u32 py = start_y; py < end_y; py ++ )
  44         {
  45                 trace_origin[1] = csr_lerpf( cam_bounds[1], cam_bounds[3], (float)py/(float)y );
  46
  47                 for( u32 px = start_x; px < end_x; px ++ )
  48                 {
  49                         trace_origin[0] = csr_lerpf( cam_bounds[0], cam_bounds[2], (float)px/(float)x );
  50
  51                         csr_frag *frag = &fragments[ py*y + px ];
  52
  53                         float tqa = 0.f, tqb = 0.f;
  54                         float tdepth = csr_ray_tri( trace_origin, trace_dir, tri[0].co, tri[1].co, tri[2].co, &tqa, &tqb );
  55
  56                         if( tdepth < frag->depth )
  57                         {
  58                                 frag->depth = tdepth;
  59                                 frag->id = id;
  60                                 frag->qa = tqa;
  61                                 frag->qb = tqb;
  62                         }
  63                 }
  64         }
  65 }
  66
  67 // First pass 'fragmentize'
  68 void draw_buffers( csr_frag fragments[], u32 x, u32 y, v4f cam_bounds, vmf_vert *triangles, u32 triangle_count )
  69 {
  70         for( u32 i = 0; i < triangle_count; i ++ )
  71         {
  72                 vmf_vert *triangle = triangles + i*3;
  73                 simple_raster( fragments, x, y, cam_bounds, triangle, i );
  74         }
  75 }