shaderlib: Add smart_denoise function, add example, move example images into separate folder; implements #29

shaderlib/denoise.gdshaderinc

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+
+/* glslSmartDenoise by Michele Morrone, adapted
+original code: https://github.com/BrutPitt/glslSmartDeNoise
+license of the original code:
+BSD 2-Clause License
+
+Copyright (c) 2019-2020 Michele Morrone
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+#define INV_SQRT_OF_2PI 0.39894228040143267793994605993439  // 1.0/SQRT_OF_2PI
+#define INV_PI 0.31830988618379067153776752674503
+
+vec4 smart_denoise(sampler2D tex, vec2 uv, float sigma, float kSigma, float threshold) {
+	float radius = round(kSigma*sigma);
+	float radQ = radius * radius;
+
+	float invSigmaQx2 = .5 / (sigma * sigma);      // 1.0 / (sigma^2 * 2.0)
+	float invSigmaQx2PI = INV_PI * invSigmaQx2;    // 1/(2 * PI * sigma^2)
+
+	float invThresholdSqx2 = .5 / (threshold * threshold);     // 1.0 / (sigma^2 * 2.0)
+	float invThresholdSqrt2PI = INV_SQRT_OF_2PI / threshold;   // 1.0 / (sqrt(2*PI) * sigma^2)
+
+	vec4 centrPx = texture(tex,uv);
+
+	float zBuff = 0.0;
+	vec4 aBuff = vec4(0.0);
+	vec2 size = vec2(textureSize(tex, 0));
+
+	for (float dx = -radius; dx <= radius; dx++) {
+		float pt = sqrt(radQ - dx * dx);       // pt = yRadius: have circular trend
+		for (float dy = -pt; dy <= pt; dy++) {
+			vec2 d = vec2(dx, dy);
+			float blurFactor = exp( -dot(d, d) * invSigmaQx2 ) * invSigmaQx2PI;
+
+			vec4 walkPx =  texture(tex,uv+d/size);
+			vec4 dC = walkPx-centrPx;
+			float deltaFactor = exp(-dot(dC, dC) * invThresholdSqx2) * invThresholdSqrt2PI * blurFactor;
+
+			zBuff += deltaFactor;
+			aBuff += deltaFactor*walkPx;
+		}
+	}
+	return aBuff/zBuff;
+}