一段水波纹的shader

【核心代码】

precision mediump float;

//uniform sampler2D usTexture;

varying vec2 vTexCoord;

//uniform int isHighPrecision;
uniform sampler2D heightCurrentSampler;
uniform float fNormalScale;
//uniform vec4 texture_size;
uniform float inverseViewportWidth;
uniform float inverseViewportHeight;

float DecodeHeightmap(vec4 heightmap)
{
vec4 table;

//if ( isHighPrecision == 1 )
// table = vec4(1.0, -1.0, 1.0/256.0, -1.0/256.0);
//else
table = vec4(1.0, -1.0, 0.0, 0.0);

return dot(heightmap, table);
}


float DecodeHeightmap(sampler2D heightmapSampler, vec2 texcoord)
{
vec4 heightmap = texture2D(heightmapSampler, texcoord);
return DecodeHeightmap(heightmap);
}

void main() {
vec2 offset[4];
offset[0] = vec2(-1.0, 0.0);
offset[1] = vec2( 1.0, 0.0);
offset[2] = vec2( 0.0,-1.0);
offset[3] = vec2( 0.0, 1.0);

vec2 inverseViewportSize = vec2(inverseViewportWidth, inverseViewportHeight);

float fHeightL = DecodeHeightmap(heightCurrentSampler, vTexCoord offset[0]*inverseViewportSize);
float fHeightR = DecodeHeightmap(heightCurrentSampler, vTexCoord offset[1]*inverseViewportSize);
float fHeightT = DecodeHeightmap(heightCurrentSampler, vTexCoord offset[2]*inverseViewportSize);
float fHeightB = DecodeHeightmap(heightCurrentSampler, vTexCoord offset[3]*inverseViewportSize);


//vec3 n = vec3(fHeightR - fHeightL,fHeightB - fHeightT,fNormalScale);
//vec3 normal = (n 1.0) * 0.5;
gl_FragColor = vec4(fHeightR - fHeightL, fHeightB - fHeightT, fNormalScale, 1.0);

/*
//float s_offset = (fHeightB - fHeightT) / 2048.0;
//float t_offset = (fHeightL - fHeightR) / 2048.0;
float s_offset = (fHeightB - fHeightT) / 1.0;
float t_offset = (fHeightL - fHeightR) / 1.0;
float clampFactor = 0.5;
s_offset = (s_offset < -clampFactor) ? -clampFactor : s_offset;
t_offset = (t_offset < -clampFactor) ? -clampFactor : t_offset;
s_offset = (s_offset > clampFactor) ? clampFactor : s_offset;
t_offset = (t_offset > clampFactor) ? clampFactor : t_offset;

gl_FragColor = vec4(s_offset, t_offset, 0.0, 0.0);
*/


}