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Gamma correction, quadratic light falloff, and randomness improvements. #1

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Gamma correction, quadratic light falloff, and randomness improvements. #1

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23 changes: 15 additions & 8 deletions webgl-path-tracing.js
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,9 @@
// shader strings
////////////////////////////////////////////////////////////////////////////////

var gamma = 2.2;
var invGamma = 1/gamma;

// vertex shader for drawing a textured quad
var renderVertexSource =
' attribute vec3 vertex;' +
Expand All @@ -46,6 +49,7 @@ var renderFragmentSource =
' uniform sampler2D texture;' +
' void main() {' +
' gl_FragColor = texture2D(texture, texCoord);' +
' gl_FragColor.rgb = pow( gl_FragColor.rgb*0.7, vec3( ' + invGamma + ' ) );' +
' }';

// vertex shader for drawing a line
Expand Down Expand Up @@ -145,8 +149,11 @@ var normalForSphereSource =

// use the fragment position for randomness
var randomSource =
' float random(vec3 scale, float seed) {' +
' return fract(sin(dot(gl_FragCoord.xyz + seed, scale)) * 43758.5453 + seed);' +
' highp float random(highp vec3 scale, float seed) {' +
' highp float d = 43758.5453;' +
' highp float dt = dot(gl_FragCoord.xyz + seed,scale);' +
' highp float sn = mod(dt,3.1415926);' +
' return fract(sin(sn) * d);' +
' }';

// random cosine-weighted distributed vector
Expand Down Expand Up @@ -208,12 +215,12 @@ var newGlossyRay =
' specularHighlight = pow(specularHighlight, 3.0);';

var yellowBlueCornellBox =
' if(hit.x < -0.9999) surfaceColor = vec3(0.1, 0.5, 1.0);' + // blue
' else if(hit.x > 0.9999) surfaceColor = vec3(1.0, 0.9, 0.1);'; // yellow
' if(hit.x < -0.9999) surfaceColor = pow(vec3(0.1, 0.5, 1.0), vec3(' + gamma + '));' + // blue
' else if(hit.x > 0.9999) surfaceColor = pow(vec3(1.0, 0.9, 0.1), vec3(' + gamma + '));'; // yellow

var redGreenCornellBox =
' if(hit.x < -0.9999) surfaceColor = vec3(1.0, 0.3, 0.1);' + // red
' else if(hit.x > 0.9999) surfaceColor = vec3(0.3, 1.0, 0.1);'; // green
' if(hit.x < -0.9999) surfaceColor = pow(vec3(1.0, 0.3, 0.1), vec3(' + gamma + '));' + // red
' else if(hit.x > 0.9999) surfaceColor = pow(vec3(0.3, 1.0, 0.1), vec3(' + gamma + '));'; // green

function makeShadow(objects) {
return '' +
Expand Down Expand Up @@ -261,7 +268,7 @@ function makeCalculateColor(objects) {

// compute diffuse lighting contribution
' vec3 toLight = light - hit;' +
' float diffuse = max(0.0, dot(normalize(toLight), normal));' +
' float diffuse = max(0.0, dot(normalize(toLight), normal))/dot(toLight,toLight);' +

// trace a shadow ray to the light
' float shadowIntensity = shadow(hit + normal * ' + epsilon + ', toLight);' +
Expand Down Expand Up @@ -712,7 +719,7 @@ PathTracer.prototype.update = function(matrix, timeSinceStart) {
this.uniforms.ray01 = getEyeRay(matrix, -1, +1);
this.uniforms.ray10 = getEyeRay(matrix, +1, -1);
this.uniforms.ray11 = getEyeRay(matrix, +1, +1);
this.uniforms.timeSinceStart = timeSinceStart;
this.uniforms.timeSinceStart = ( timeSinceStart % 46735.275 ) / 1000; // prevent huge values being crunched in the shader
this.uniforms.textureWeight = this.sampleCount / (this.sampleCount + 1);

// set uniforms
Expand Down