NV_shadow_samplers_cube

GL_NV_shadow_samplers_cube

Mathias Heyer, NVIDIA
Greg Roth, NVIDIA

Greg Roth, NVIDIA (groth 'at' nvidia 'dot' com)

Complete

Date: Aug 30, 2012
Revision: 4

OpenGL ES Extension #147

Requires OpenGL ES 2.0.

Written based on the wording of the OpenGL ES 2.0.25 Specification.

Written based on the wording of The OpenGL ES Shading Language
1.00.14 Specification.

Requires OES_depth_texture_cube_map and EXT_shadow_samplers.

This extension expands the shadow map capability described in
EXT_shadow_samplers to include support for shadow samplers of cube
map textures.

None

Returned in <type> by glGetActiveUniform:

    GL_SAMPLER_CUBE_SHADOW_NV                       0x8DC5

#define GL_NV_shadow_samplers_cube 1

samplerCubeShadowNV

float shadowCubeNV(samplerCubeShadowNV sampler, vec4 coord);

Modify Section 2.10.4 (Shader Variables)

In the final sentence on p. 36 add "SAMPLER_CUBE_SHADOW_NV" to the
list of types that can be returned in the <type> parameter of
GetActiveUniform.

Modify Section 4.1, (Basic Types):

Append the following row to the unnamed table in section 4.1

Type                 Meaning
---------------      ---------------------------------------------------------
samplerCubeShadowNV  a handle for accessing a Cube depth texture with comparison


Modify section 4.5.3 (Default Precision Qualifiers):

Add to the list of predeclared globally scoped default precision
statements:

"precision lowp samplerCubeShadowNV;"

Modify section 8.7 (Texture Lookup Functions):

Add the following new texture lookup function:

The built-in texture lookup function shadowCubeNV is optional,
and must be enabled by

#extension GL_NV_shadow_samplers_cube : enable

before being used.

Syntax:

    float shadowCubeNV(samplerCubeShadowNV sampler, vec4 coord)

Description:

Use texture coordinate (coord.s, coord.t, coord.p) to do a depth
comparison lookup on the depth cubemap bound to sampler, as
described in section 3.7.14.1. The direction of the vector (coord.s,
coord.t, coord.p) is used to select which face to do a two-
dimensional texture lookup in, as described in section 3.7.5 of the
OpenGL ES 2.0 specification. The fourth component of coord (coord.q)
is used as the R value. The texture bound to sampler must be a depth
cubemap, otherwise results are undefined.

(1) Should the result of the texture comparison be interpreted as
a LUMINANCE, INTENSITY or ALPHA texel?

RESOLVED: A scalar value is returned from the shadow lookup built-in
function in the fragment shader, so it can be interpreted however desired.

Rev.    Date        Author      Changes
----  ------------- ---------   ----------------------------------------
 4    30 Aug 2012    groth      Added missing NV suffixes
 3    28 Aug 2012    groth      Minor copy edits
 2    19 Aug 2012    groth      Correct dependency and GLSL enable
 1    12 Aug 2012    groth      Initial GLES2 version from EXT_gpu_shader4.