32testgradient.fs

#version 460 core
in vec2 TexCoords;
uniform sampler2D uv0;//tex1
out vec3 uv1;//tex1
//the pressure is stored in the z conponent of uv0 and uv1
//uv0 is GL_TEXTURE1  UV0 IS GL_TEXTURE0 color attachment1
void main()
{
	vec3 uv=vec3(texture(uv0,TexCoords));
	//float pl,pr,pt,pb;

	//zuo pl
	//vec3 oldpos=vec3(gl_FragCoord.x-1.0,gl_FragCoord.y,gl_FragCoord.z);
	//vec2 oldtexcoord=vec2((oldpos.x-0.5)/799.0,(oldpos.y-0.5)/599.0);

	    
		//oldpos=vec3(gl_FragCoord.x-1.0,gl_FragCoord.y,gl_FragCoord.z);
	
		//oldtexcoord=vec2(oldpos.x/799.5,oldpos.y/599.5);
		//oldtexcoord=vec2(oldpos.x/799.5,oldpos.y/799.5);
		//pl=texture(uv0,oldtexcoord).z; //zuo

		//you pr
		//oldpos=vec3(gl_FragCoord.x+1.0,gl_FragCoord.y,gl_FragCoord.z);
		
		//oldtexcoord=vec2(oldpos.x/799.5,oldpos.y/599.5);
		//oldtexcoord=vec2(oldpos.x/799.5,oldpos.y/799.5);
		//pr=texture(uv0,oldtexcoord).z; //you

		//shang pt
		//oldpos=vec3(gl_FragCoord.x,gl_FragCoord.y+1.0,gl_FragCoord.z);
	
		//oldtexcoord=vec2(oldpos.x/799.5,oldpos.y/599.5);
		//oldtexcoord=vec2(oldpos.x/799.5,oldpos.y/799.5);
		//pt=texture(uv0,oldtexcoord).z; //shang

		//xia pb
		//oldpos=vec3(gl_FragCoord.x,gl_FragCoord.y-1.0,gl_FragCoord.z);
	
		//oldtexcoord=vec2(oldpos.x/799.5,oldpos.y/599.5);
		//oldtexcoord=vec2(oldpos.x/799.5,oldpos.y/799.5);
		//pt=texture(uv0,oldtexcoord).z; //xia

	vec2 xoffset=vec2(1.0/800.0,0.0);
	vec2 yoffset=vec2(0.0,1.0/800.0);

	float pl=texture(uv0,TexCoords-xoffset).z;
	float pr=texture(uv0,TexCoords+xoffset).z;
	float pt=texture(uv0,TexCoords+yoffset).z;
	float pb=texture(uv0,TexCoords-yoffset).z;
		
	vec2 g=vec2(0.5*(pr-pl),0.5*(pt-pb));
		//uv1=vec3(g,uv.z);
		//if(gl_FragCoord.x==799.5)
			//g.y=0.0;
	uv1=vec3(g.x,g.y,uv.z);
}