Add slang shaders for additional samples

shaders/slang/pbrtexture/skybox.slang

@@ -0,0 +1,70 @@
+/* Copyright (c) 2025, Sascha Willems
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ */
+
+struct VSInput
+{
+    float3 Pos;
+    float3 Normal;
+    float2 UV;
+};
+
+struct VSOutput
+{
+    float4 Pos : SV_POSITION;
+    float3 UVW;
+};
+
+struct UBO
+{
+    float4x4 projection;
+    float4x4 model;
+};
+ConstantBuffer<UBO> ubo;
+
+struct UBOParams {
+	float4 lights[4];
+	float exposure;
+	float gamma;
+};
+ConstantBuffer<UBOParams> uboParams;
+
+SamplerCube samplerEnv;
+
+// From http://filmicworlds.com/blog/filmic-tonemapping-operators/
+float3 Uncharted2Tonemap(float3 color)
+{
+	float A = 0.15;
+	float B = 0.50;
+	float C = 0.10;
+	float D = 0.20;
+	float E = 0.02;
+	float F = 0.30;
+	float W = 11.2;
+	return ((color*(A*color+C*B)+D*E)/(color*(A*color+B)+D*F))-E/F;
+}
+
+[shader("vertex")]
+VSOutput vertexMain(VSInput input)
+{
+    VSOutput output;
+    output.UVW = input.Pos;
+    output.Pos = mul(ubo.projection, mul(ubo.model, float4(input.Pos.xyz, 1.0)));
+    return output;
+}
+
+[shader("fragment")]
+float4 fragmentMain(VSOutput input)
+{
+    float3 color = samplerEnv.Sample(input.UVW).rgb;
+
+	// Tone mapping
+	color = Uncharted2Tonemap(color * uboParams.exposure);
+	color = color * (1.0f / Uncharted2Tonemap((11.2f).xxx));
+	// Gamma correction
+	color = pow(color, (1.0f / uboParams.gamma).xxx);
+
+	return float4(color, 1.0);
+}