spark/src/shaders/splatFragment.glsl

precision highp float;
precision highp int;

#include <splatDefines>

uniform float near;
uniform float far;
uniform bool encodeLinear;
uniform float maxStdDev;
uniform bool disableFalloff;
uniform float falloff;

uniform bool splatTexEnable;
uniform sampler3D splatTexture;
uniform mat2 splatTexMul;
uniform vec2 splatTexAdd;
uniform float splatTexNear;
uniform float splatTexFar;
uniform float splatTexMid;

out vec4 fragColor;

in vec4 vRgba;
in vec2 vSplatUv;
in vec3 vNdc;

void main() {
    vec4 rgba = vRgba;

    float z = dot(vSplatUv, vSplatUv);
    if (!splatTexEnable) {
        if (z > (maxStdDev * maxStdDev)) {
            discard;
        }
    } else {
        vec2 uv = splatTexMul * vSplatUv + splatTexAdd;
        float ndcZ = vNdc.z;
        float depth = (2.0 * near * far) / (far + near - ndcZ * (far - near));
        float clampedFar = max(splatTexFar, splatTexNear);
        float clampedDepth = clamp(depth, splatTexNear, clampedFar);
        float logDepth = log2(clampedDepth + 1.0);
        float logNear = log2(splatTexNear + 1.0);
        float logFar = log2(clampedFar + 1.0);

        float texZ;
        if (splatTexMid > 0.0) {
            float clampedMid = clamp(splatTexMid, splatTexNear, clampedFar);
            float logMid = log2(clampedMid + 1.0);
            texZ = (clampedDepth <= clampedMid) ?
                (0.5 * ((logDepth - logNear) / (logMid - logNear))) :
                (0.5 * ((logDepth - logMid) / (logFar - logMid)) + 0.5);
        } else {
            texZ = (logDepth - logNear) / (logFar - logNear);
        }

        vec4 modulate = texture(splatTexture, vec3(uv, 1.0 - texZ));
        rgba *= modulate;
    }

    rgba.a *= mix(1.0, exp(-0.5 * z), falloff);

    if (rgba.a < MIN_ALPHA) {
        discard;
    }
    if (encodeLinear) {
        rgba.rgb = srgbToLinear(rgba.rgb);
    }
    fragColor = rgba;
}