Show texel border and more swizzle options

GlitchyEditor/resources/Shaders/RenderTargetGroupViewer.fx

@@ -1,3 +1,5 @@
+#include "ShaderHelpers.hlsl"
+
 Texture2DArray Texture : register(t0);
 SamplerState Sampler : register(s0);
 
@@ -7,11 +9,16 @@ SamplerState IntSampler : register(s1);
 Texture2DArray<uint4> UIntTexture : register(t2);
 SamplerState UIntSampler : register(s2);
 
-#define SWIZZLE_NONE 0
+#define SWIZZLE_ZERO 0
-#define SWIZZLE_R 1
+#define SWIZZLE_ONE 1
-#define SWIZZLE_G 2
+#define SWIZZLE_R 2
-#define SWIZZLE_B 3
+#define SWIZZLE_G 3
-#define SWIZZLE_A 4
+#define SWIZZLE_B 4
+#define SWIZZLE_A 5
+#define SWIZZLE_ONE_MINUS_R 6
+#define SWIZZLE_ONE_MINUS_G 7
+#define SWIZZLE_ONE_MINUS_B 8
+#define SWIZZLE_ONE_MINUS_A 9
 
 cbuffer Constants
 {
@@ -31,6 +38,9 @@ cbuffer Constants
     float2 Texels;
 
     float4x4 WorldViewProjection;
+
+    bool ShowTexelBorders = true;
+    float TexelBorderCutoff = 10;
 }
 
 struct VS_Input
@@ -59,6 +69,12 @@ void SwizzleColor(int swizzleMode, float4 colorToSwizzle, inout float output)
 {
     switch (swizzleMode)
     {
+	    case SWIZZLE_ZERO:
+            output = 0.0;
+            break;
+	    case SWIZZLE_ONE:
+            output = 1.0;
+            break;
 	    case SWIZZLE_R:
             output = colorToSwizzle.r;
             break;
@@ -70,31 +86,77 @@ void SwizzleColor(int swizzleMode, float4 colorToSwizzle, inout float output)
             break;
 	    case SWIZZLE_A:
             output = colorToSwizzle.a;
+            break;
+	    case SWIZZLE_ONE_MINUS_R:
+            output = 1.0 - colorToSwizzle.r;
+            break;
+	    case SWIZZLE_ONE_MINUS_G:
+            output = 1.0 - colorToSwizzle.g;
+            break;
+	    case SWIZZLE_ONE_MINUS_B:
+            output = 1.0 - colorToSwizzle.b;
+            break;
+	    case SWIZZLE_ONE_MINUS_A:
+            output = 1.0 - colorToSwizzle.a;
             break;
 		default:
             break;
     }
 }
 
+/**
+ * Returns whether or not the current pixel lies on the border between two texels.
+ */
+void ApplyTexelBorder(float2 texelPosition, inout float4 color)
+{
+    // Calculate derivatives of texelPosition -> how many texels to we move if we move one pixel in x/y direction
+    float2 dudx = ddx(texelPosition);
+    float2 dudy = ddy(texelPosition);
+
+    // This is the reciprocal of the screen size of one texel.
+    float grad = float2(length(dudx), length(dudy));
+    
+    float2 pixelsPerTexel = 1.0f / grad;
+
+    // Threshold is half the size of a screen pixel in texel-space.
+    float2 threshold = grad / 2.0f;
+
+    // Calculate the distance between the screen pixel and the texel border in texels.
+    float2 fracPart = frac(texelPosition);
+    float2 distanceToBorder = min(fracPart, 1.0 - fracPart);
+    
+    if (any(distanceToBorder < threshold))
+    {
+        // Ensure the border is always at least 0.5 luminance away from the texel.
+        // TODO: This can flicker while moving/zooming, because we are by design on a texel border!
+        float luminance = ColorToLuminance(color.rgb);
+        float4 borderColor = (luminance > 0.5f) ? float4(0, 0, 0, 1) : float4(1, 1, 1, 1);
+
+        color = lerp(color, borderColor, clamp((min(pixelsPerTexel.x, pixelsPerTexel.y) - TexelBorderCutoff / 2.0) / TexelBorderCutoff, 0.0f, 0.8f));
+    }
+}
+
 float4 PS(PS_Input input) : SV_Target0
 {
     float4 outputColor;
 
+    float2 texelPosition = input.Texcoord * Texels;
+
     if (Mode == 0)
     {
         //float4 color = Texture.SampleLevel(Sampler, float3(input.Texcoord, ArraySlice), MipLevel);
         // Quasi next neighbor
-        float4 color = Texture.Load(int4(input.Texcoord * Texels, ArraySlice, MipLevel));
+        float4 color = Texture.Load(int4(texelPosition, ArraySlice, MipLevel));
         outputColor = float4(ColorOffset.xxx, AlphaOffset) + color * float4(ColorScale.xxx, AlphaScale);
     }
     else if (Mode == 1)
     {
-        int4 color = IntTexture.Load(int4(input.Texcoord * Texels, ArraySlice, MipLevel));
+        int4 color = IntTexture.Load(int4(texelPosition, ArraySlice, MipLevel));
         outputColor = float4(ColorOffset.xxx, AlphaOffset) + color * float4(ColorScale.xxx, AlphaScale);
     }
     else if (Mode == 2)
     {
-        uint4 color = UIntTexture.Load(int4(input.Texcoord * Texels, ArraySlice, MipLevel));
+        uint4 color = UIntTexture.Load(int4(texelPosition, ArraySlice, MipLevel));
         outputColor = float4(ColorOffset.xxx, AlphaOffset) + color * float4(ColorScale.xxx, AlphaScale);
     }
 
@@ -105,6 +167,11 @@ float4 PS(PS_Input input) : SV_Target0
     SwizzleColor(Swizzle.b, outputColor, swizzledOutput.b);
     SwizzleColor(Swizzle.a, outputColor, swizzledOutput.a);
 
+    if (ShowTexelBorders)
+    {
+        ApplyTexelBorder(texelPosition, swizzledOutput);
+    }
+
     return swizzledOutput;
 }
 

GlitchyEditor/src/EditWindows/AssetViewer.bf

@@ -152,11 +152,16 @@ class TextureViewer
 
 	enum ColorChannelSwizzle : int32
 	{
-		None,
+		Zero,
+		One,
 		R,
 		G,
 		B,
-		A
+		A,
+		OneMinusR,
+		OneMinusG,
+		OneMinusB,
+		OneMinusA
 	}
 
 	AssetHandle<Effect> _effect;
@@ -164,6 +169,7 @@ class TextureViewer
 	Material _renderTargetMaterial ~ _.ReleaseRef();
 
 	float _zoom = 1.0f;
+	bool _showTexelBorder = false;
 
 	BackgroundMode _backgroundMode = .Checkerboard;
 	ColorRGBA _backgroundColor;
@@ -171,10 +177,6 @@ class TextureViewer
 	SampleMode _sampleMode = .Linear;
 
 	RenderTargetGroup _targets ~ _?.ReleaseRef();
-	/*RenderTarget2D _target ~ _?.ReleaseRef();
-	RenderTarget2D _idTarget ~ _?.ReleaseRef();
-	// TODO: we don't need depth!
-	DepthStencilTarget _depth ~ _?.ReleaseRef();*/
 
 	public this()
 	{
@@ -281,8 +283,6 @@ class TextureViewer
 
 		if (ImGui.CollapsingHeader("Color and Transparency"))
 		{
-			ImGui.TextUnformatted("Channel Swizzle:");
-
 			if (ImGui.BeginTable("ColorAndAlpha", 4))
 			{
 				ImGui.TableNextRow();
@@ -338,6 +338,10 @@ class TextureViewer
 			
 			ImGui.Separator();
 
+			ImGui.Checkbox("Show texel grid", &_showTexelBorder);
+
+			ImGui.Separator();
+
 			ImGui.TextUnformatted("Channel Swizzle:");
 
 			if (ImGui.BeginTable("SwizzleTable", 9))
@@ -376,6 +380,12 @@ class TextureViewer
 		
 		if (ImGui.BeginCombo(scope $"##swizzle{text}", scope $"{swizzle}"))
 		{
+			if (ImGui.Selectable("0", swizzle == .Zero))
+				swizzle = .Zero;
+
+			if (ImGui.Selectable("1", swizzle == .One))
+				swizzle = .One;
+
 			if (ImGui.Selectable("R", swizzle == .R))
 				swizzle = .R;
 
@@ -388,8 +398,17 @@ class TextureViewer
 			if (ImGui.Selectable("A", swizzle == .A))
 				swizzle = .A;
 			
-			if (ImGui.Selectable("None", swizzle == .None))
+			if (ImGui.Selectable("1 - R", swizzle == .OneMinusR))
-				swizzle = .None;
+				swizzle = .OneMinusR;
+			
+			if (ImGui.Selectable("1 - G", swizzle == .OneMinusG))
+				swizzle = .OneMinusG;
+
+			if (ImGui.Selectable("1 - B", swizzle == .OneMinusB))
+				swizzle = .OneMinusB;
+			
+			if (ImGui.Selectable("1 - A", swizzle == .OneMinusA))
+				swizzle = .OneMinusA;
 
 			ImGui.EndCombo();
 		}
@@ -590,10 +609,6 @@ class TextureViewer
 			viewedTexture.SamplerState = SamplerStateManager.LinearClamp;
 		}*/
 
-		//Renderer2D.BeginScene(_camera, .SortByTexture, _effect);
-
-		// float3(_position * .(1, -1), 0)
-		//RenderCommand.Clear(_depth, .Depth, 1.0f, 0);
 		RenderCommand.Clear(_targets, .Depth);
 
 		Matrix matrix = .Translation(float3((_position + float2(_targets.Width, _targets.Height) / 2) * .(1, -1), 0)) * .Scaling(float3(zoomedTextureSize, 1));
@@ -610,6 +625,9 @@ class TextureViewer
 
 		_renderTargetMaterial.SetVariable("Swizzle", int4((int32)_swizzleR, (int32)_swizzleG, (int32)_swizzleB, (int32)_swizzleA));
 		
+		_renderTargetMaterial.SetVariable("ShowTexelBorders", _showTexelBorder);
+		_renderTargetMaterial.SetVariable("TexelBorderCutoff", 10.0f);
+
 		int textureSlot = -1;
 
 		if (format.IsInt())