GLSL built-in function
texelFetchOffset()
Fetches a texel with an additional constant integer offset.
Demo version: GLSL ES 3.00 / WebGL 2Demo stage: Fragment
Syntax
gvec4 texelFetchOffset(gsampler2D sampler, ivec2 coord, int lod, ivec2 offset)Parameters
- sampler
- Bound fixture texture
- coord
- Lookup coordinate
- lod
- Mip level; zero is full resolution
- offset
- Compile-time constant texel offset
Return value
The four components of the texel at coord + offset in the selected mip level, without interpolation.
Live example
Edit the code and the preview updates as you type.
What texelFetchOffset does
Fetches a texel with an additional constant integer offset.
Read the preview
The base address ivec2(uv*251.0)+ivec2(2) leaves room for the constant ivec2(1,0) offset. Change that offset to ivec2(-1,0) to read two texels farther left while remaining in bounds.
Core call
texelFetchOffset(u_texture,ivec2(uv*251.0)+ivec2(2),0,ivec2(1,0)).rgb;
offset must be a constant expression within the implementation limits.
Experiment
Set the final offset argument to ivec2(0,1). Sampling moves from the right neighbor to the upper neighbor of the base address, which shifts the grid's registration on screen.