Added slang shaders for compute nbody sample

shaders/slang/computenbody/particle.slang

@@ -0,0 +1,56 @@
+/* Copyright (c) 2025, Sascha Willems
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ */
+
+struct VSInput
+{
+    float4 Pos;
+    float4 Vel;
+};
+
+struct VSOutput
+{
+    float4 Pos : SV_POSITION;
+    float PSize : SV_PointSize;
+    float GradientPos;
+    float2 CenterPos;
+    float PointSize;
+};
+
+Sampler2D samplerColorMap;
+Sampler2D samplerGradientRamp;
+
+struct UBO
+{
+    float4x4 projection;
+    float4x4 modelview;
+    float2 screendim;
+};
+ConstantBuffer<UBO> ubo;
+
+[shader("vertex")]
+VSOutput vertexMain(VSInput input)
+{
+    VSOutput output;
+    const float spriteSize = 0.005 * input.Pos.w; // Point size influenced by mass (stored in input.Pos.w);
+
+    float4 eyePos = mul(ubo.modelview, float4(input.Pos.x, input.Pos.y, input.Pos.z, 1.0));
+    float4 projectedCorner = mul(ubo.projection, float4(0.5 * spriteSize, 0.5 * spriteSize, eyePos.z, eyePos.w));
+    output.PSize = output.PointSize = clamp(ubo.screendim.x * projectedCorner.x / projectedCorner.w, 1.0, 128.0);
+
+    output.Pos = mul(ubo.projection, eyePos);
+    output.CenterPos = ((output.Pos.xy / output.Pos.w) + 1.0) * 0.5 * ubo.screendim;
+
+    output.GradientPos = input.Vel.w;
+    return output;
+}
+
+[shader("fragment")]
+float4 fragmentMain(VSOutput input)
+{
+    float3 color = samplerGradientRamp.Sample(float2(input.GradientPos, 0.0)).rgb;
+    float2 PointCoord = (input.Pos.xy - input.CenterPos.xy) / input.PointSize + 0.5;
+    return float4(samplerColorMap.Sample(PointCoord).rgb * color, 1);
+}