opengl es - How to emulate GL_DEPTH_CLAMP_NV? -

i have platform extension not available ( non nvidia ). how emulate functionality ? need solve far plane clipping problem when rendering stencil shadow volumes z-fail algorithm.

since you're using opengl es, mentioned trying clamp gl_fragdepth, i'm assuming you're using opengl es 2.0, here's shader trick:

you can emulate arb_depth_clamp using separate varying z-component.

vertex shader:

varying float z; void main() {     gl_position = ftransform();      // transform z window coordinates     z = gl_position.z / gl_position.w;     z = (gl_depthrange.diff * z + gl_depthrange.near + gl_depthrange.far) * 0.5;      // prevent z-clipping     gl_position.z = 0.0; } 

fragment shader:

varying float z; void main() {     gl_fragcolor = vec4(vec3(z), 1.0);     gl_fragdepth = clamp(z, 0.0, 1.0); }