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/* Shader for bilinear filtering of textures during drawing.
* This is a "manual" do-it-yourself implementation of the standard GL_LINEAR bilinear
* texture filtering mode of the GPU. Normally you won't need it, because the hardware
* does this automatically (and faster). But some hardware (e.g., ATI X1000 series)
* can't do automatic filtering on floating point textures, so we need a manual
* implementation to support floating point texture filtering on such GPU's.
*
* This code is just here as a reference. PTB has the same code built into Screen().
*
* (w)2007 by Mario Kleiner. Licensed under MIT license.
*/
#extension GL_ARB_texture_rectangle : enable
uniform sampler2DRect Image;
void main()
{
/* Get wanted texture coordinate for which we should filter: */
vec2 texinpos = (gl_TexCoord[0].st) - vec2(0.5, 0.5);
/* Retrieve texel colors for 4 nearest neighbours: */
vec4 tl=texture2DRect(Image, floor(texinpos));
vec4 tr=texture2DRect(Image, floor(texinpos) + vec2(1.0, 0.0));
vec4 bl=texture2DRect(Image, floor(texinpos) + vec2(0.0, 1.0));
vec4 br=texture2DRect(Image, floor(texinpos) + vec2(1.0, 1.0));
/* Perform weighted linear interpolation -- bilinear interpolation of the 4: */
tl=mix(tl,tr,fract(texinpos.x));
bl=mix(bl,br,fract(texinpos.x));
vec4 texcolor = mix(tl, bl, fract(texinpos.y));
/* Multiply filtered texcolor with incoming fragment color (GL_MODULATE emulation): */
/* Assign result as output fragment color: */
gl_FragColor = texcolor * gl_Color;
}
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