sampleSourcePixel
sampleSourcePixel: undefined | string
If the fragment shader shifts pixels from their original locations, then by default element locate will not work, because it expects the pixels produced by an element
to remain at their original locations. This can be fixed by supplying the body of a GLSL function vec4 sampleSourcePixel() that, as part of the fragment shader,
obtains the pixel in the source image corresponding to the pixel that will be output by the shader.
For example, if the source pixel is simply specified by a varying vec2 v_texCoord computed by the vertex shader, then this property should be defined as return TEXTURE(u_diffuse, v_texCoord);.
This function will automatically be included in the fragment shader, so it can also be used by effectMain when computing the output color.
note sampleSourcePixel should not modify the sample in any way - that should be done only in effectMain.
note sampleSourcePixel should not be supplied if the effect does not shift pixels as it can negatively impact performance of element locate.
see FlipImageEffect or LensDistortionEffect for examples of effects that implement this property.
Defined in
Last Updated: 20 June, 2023