webgl glsl emulate texture3d

问题:

I'm porting a piece of opengl to webgl and i'm trying to emulate texture3d. Somehow something is going wrong.

No interpolation is needed because it is only used for calculations. I'm not sure about the geometry part of the original code, the per layer properties are now fetched trough a texture.

Update : Ok i rewrote the texture 3d functions, I still encounter some problems :

const vec3 volumeTextureSize = vec3( 256.0, 128.0, 32.0 );
const vec2 imageSize = vec2( 1024.0, 1024.0 );

vec2 uvFromUvw( vec3 uvw ) {
    const vec3 size = volumeTextureSize;
    const vec2 layersPerDim = size.xy / imageSize.xy;
    const vec2 pixelsPerLayer = imageSize / layersPerDim;

    // normalized in
    float layer = floor(uvw.z * size.z);

    float layerX = mod(layer, layersPerDim.x);
    float layerY = floor(layer / layersPerDim.x);

    vec2 layerUv = vec2(layerX, layerY) * pixelsPerLayer;
    vec2 layerSpaceUv = (uvw.xy * size.xy) / layersPerDim;

    vec2 uv = layerSpaceUv + layerUv;

    uv /= imageSize;

    return uv;
}

vec4 texture3D( sampler2D tex, vec3 uvw ) {
    vec2 uv = uvFromUvw( uvw );
    return texture2D(tex, uv);
}

vec3 uvwFromUv( vec2 uv ) {
    const vec3 size = volumeTextureSize;
    const vec2 layersPerDim =  imageSize.xy / size.xy;
    const vec2 pixelsPerLayer = imageSize / layersPerDim;

    vec2 normUv = uv / imageSize;

    vec2 layerUv = floor(vec2(normUv * layersPerDim.xy));

    vec3 uvw = vec3(0.0);

    uvw.z = floor(layerUv.x + floor( layerUv.y * layersPerDim.x));
    uvw.xy = uv - (layerUv * pixelsPerLayer.xy);

    // normalized coords
    // uvw.xy /= size.xy;
    uvw.z /= layersPerDim.x * layersPerDim.y;

    return uvw;
}

this is the original code i want to port:

glActiveTexture(GL_TEXTURE0 + deltaJUnit);
glGenTextures(1, &deltaJTexture);
glBindTexture(GL_TEXTURE_3D, deltaJTexture);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
glTexImage3D(GL_TEXTURE_3D, 0, GL_RGB16F_ARB, RES_MU_S * RES_NU, RES_MU, RES_R, 0, GL_RGB, GL_FLOAT, NULL);



    glFramebufferTextureEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, deltaJTexture, 0);

    for (int layer = 0; layer < RES_R; ++layer) {
        setLayer(jProg, layer);
        .. also set uniforms
        drawQuad();
    }

and the glsl

#ifdef _VERTEX_

void main() {
    gl_Position = gl_Vertex;
}

#endif

#ifdef _GEOMETRY_
#extension GL_EXT_geometry_shader4 : enable

void main() {
    gl_Position = gl_PositionIn[0];
    gl_Layer = layer;
    EmitVertex();
    gl_Position = gl_PositionIn[1];
    gl_Layer = layer;
    EmitVertex();
    gl_Position = gl_PositionIn[2];
    gl_Layer = layer;
    EmitVertex();
    EndPrimitive();
}

#endif