- sample_resolve = ralloc_asprintf(mem_ctx, " out_color = texelFetch(texSampler, i%s(texCoords), gl_SampleID);", texcoord_type);
+ const char *tex_coords;
+
+ if (ctx->Extensions.ARB_gpu_shader5 && samples >= 16) {
+ /* If interpolateAtOffset is available then it will be used to
+ * force the interpolation to the center. This is required at
+ * least on Intel hardware because it is possible to have a sample
+ * position on the 0 x or y axis which means it will lie exactly
+ * on the pixel boundary. If we let the hardware interpolate the
+ * coordinates at one of these positions then it is possible for
+ * it to jump to a neighboring texel when converting to ints due
+ * to rounding errors. This is only done for >= 16x MSAA because
+ * it probably has some overhead. It is more likely that some
+ * hardware will use one of these problematic positions at 16x
+ * MSAA because in that case in D3D they are defined to be at
+ * these positions.
+ */
+ tex_coords = "interpolateAtOffset(texCoords, vec2(0.0))";
+ } else {
+ tex_coords = "texCoords";
+ }
+
+ sample_resolve =
+ ralloc_asprintf(mem_ctx,
+ " out_color = texelFetch(texSampler, "
+ "i%s(%s), gl_SampleID);",
+ texcoord_type, tex_coords);
+