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#version 310 es
#extension GL_EXT_tessellation_shader : require
precision highp int;
layout(cw, quads, fractional_even_spacing) in;
layout(location = 0) patch in vec2 vOutPatchPosBase;
layout(location = 1) patch in vec4 vPatchLods;
layout(binding = 1, std140) uniform UBO
{
mat4 uMVP;
vec4 uScale;
vec2 uInvScale;
vec3 uCamPos;
vec2 uPatchSize;
vec2 uInvHeightmapSize;
};
layout(binding = 0) uniform mediump sampler2D uHeightmapDisplacement;
layout(location = 0) highp out vec3 vWorld;
layout(location = 1) highp out vec4 vGradNormalTex;
vec2 lerp_vertex(vec2 tess_coord)
{
return vOutPatchPosBase + tess_coord * uPatchSize;
}
mediump vec2 lod_factor(vec2 tess_coord)
{
mediump vec2 x = mix(vPatchLods.yx, vPatchLods.zw, tess_coord.x);
mediump float level = mix(x.x, x.y, tess_coord.y);
mediump float floor_level = floor(level);
mediump float fract_level = level - floor_level;
return vec2(floor_level, fract_level);
}
mediump vec3 sample_height_displacement(vec2 uv, vec2 off, mediump vec2 lod)
{
return mix(
textureLod(uHeightmapDisplacement, uv + 0.5 * off, lod.x).xyz,
textureLod(uHeightmapDisplacement, uv + 1.0 * off, lod.x + 1.0).xyz,
lod.y);
}
void main()
{
vec2 tess_coord = gl_TessCoord.xy;
vec2 pos = lerp_vertex(tess_coord);
mediump vec2 lod = lod_factor(tess_coord);
vec2 tex = pos * uInvHeightmapSize.xy;
pos *= uScale.xy;
mediump float delta_mod = exp2(lod.x);
vec2 off = uInvHeightmapSize.xy * delta_mod;
vGradNormalTex = vec4(tex + 0.5 * uInvHeightmapSize.xy, tex * uScale.zw);
vec3 height_displacement = sample_height_displacement(tex, off, lod);
pos += height_displacement.yz;
vWorld = vec3(pos.x, height_displacement.x, pos.y);
gl_Position = uMVP * vec4(vWorld, 1.0);
}
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