uniform float pixelGap; void main() { gl_TexCoord[0] = (vec4(gl_MultiTexCoord0) * vec4(2.0, 1.0, 1.0, 1.0)) + vec4(-0.5, 0.5, 0.0, 0.0); gl_TexCoord[1] = gl_TexCoord[0] + vec4(pixelGap, 0.0, 0.0, 0.0); gl_Position = ftransform(); }