Tiled Deferred Blending - GPU Pro: Advanced Rendering Techniques - page 304

multiple_draw_call_VS ]
attribute vec2
Position ,
TextureCoordinates ;

uniform mediump vec4
uPositionTransform ;
uniform mediump vec3
uCoordinateTransformX [ LAYER_COUNT ],
uCoordinateTransformY [ LAYER_COUNT ];

varying mediump vec2
vTextureCoordinates [ LAYER_COUNT ];

void main ()
{ gl_Position . xy =
Position . xy ￿ uPositionTransform . xy + uPositionTransform . zw ;
gl_Position . zw = vec2 ( 0.0, 1.0 );
mediump vec3 texcoord = vec3 ( TextureCoordinates ,1.0);
for ( int i =0; i < LAYER_COUNT ; i ++ )
{ vTextureCoordinates [ i ]. x =
dot ( uCoordinateTransformX [ i ], texcoord );
vTextureCoordinates [ i ]. y =
dot ( uCoordinateTransformY [ i ], texcoord );

}

}

Listing 5.1. The vertex shader.

associativity) [Forsyth 06], but care must still be taken to preserve transparency
order. The previous shader assumes that we have sorted the transparent layers
back to front.

varying mediump vec2
vTextureCoordinates [ LAYER_COUNT ];

uniform sampler2D
Textures [ LAYER_COUNT ];

void main ()
{ mediump vec4 result = vec4 ( 0.0 , 0.0, 0.0 , 0.0 ) ;

for ( int i =0; i < LAYER_COUNT ; i ++ )
{ mediump vec4 contribution =
texture2D ( Textures [ i ], vTextureCoordinates [ i ]);
result = contribution +(1.0 − contribution . a )

result ;

}

gl_FragColor = result ;

}

Listing 5.2. Multiple draw call fragment shader.