Shader debugging: scaling the world

In the linearizeDepth function in area_effect.frag, I was multiplying by 2, but the scaling of the world was off. The number I found that works best is e - 0.99, and I have no idea why.

src/main/java/com/simibubi/create/foundation/render/backend/effects/EffectsHandler.java

@@ -100,8 +100,8 @@ public class EffectsHandler {
 		program.bindDepthTexture(mainBuffer.getDepthAttachment());
 
 		GameRenderer gameRenderer = Minecraft.getInstance().gameRenderer;
-		Matrix4f projection = gameRenderer.getBasicProjectionMatrix(gameRenderer.getActiveRenderInfo(), AnimationTickHolder.getPartialTicks(), true);
+		//Matrix4f projection = gameRenderer.getBasicProjectionMatrix(gameRenderer.getActiveRenderInfo(), AnimationTickHolder.getPartialTicks(), true);
-		//Matrix4f projection = Backend.projectionMatrix.copy();
+		Matrix4f projection = Backend.projectionMatrix.copy();
 		//projection.a23 = projection.a32 = 0;
 		projection.a33 = 1;
 		projection.invert();
@@ -117,6 +117,9 @@ public class EffectsHandler {
 //		Vector3d pos3 = new Vector3d(906, 84, -207);
 		Vector3d cameraPos = gameRenderer.getActiveRenderInfo().getProjectedView();
 
+		program.setTestParam((float) (Math.E - 0.99));
+		program.setCameraPos(cameraPos.inverse());
+
 		for (int i = 0; i < 16; i++) {
 			double angle = (Math.PI * AnimationTickHolder.getRenderTime() / 40) + i * Math.PI / 4;
 

src/main/java/com/simibubi/create/foundation/render/backend/effects/SphereFilterProgram.java

@@ -39,6 +39,9 @@ public class SphereFilterProgram extends GlProgram {
 
 	protected final int uNearPlane;
 	protected final int uFarPlane;
+
+	protected final int uCameraPos;
+	protected final int testParam;
 //	protected final int uSphereCenter;
 //	protected final int uSphereRadius;
 //	protected final int uSphereFeather;
@@ -62,6 +65,8 @@ public class SphereFilterProgram extends GlProgram {
 		uInverseView = getUniformLocation("uInverseView");
 		uNearPlane = getUniformLocation("uNearPlane");
 		uFarPlane = getUniformLocation("uFarPlane");
+		uCameraPos = getUniformLocation("uCameraPos");
+		testParam = getUniformLocation("testParam");
 //
 //		uSphereCenter = getUniformLocation("uSphereCenter");
 //		uSphereRadius = getUniformLocation("uSphereRadius");
@@ -82,6 +87,14 @@ public class SphereFilterProgram extends GlProgram {
 		GL20.glUniform1f(uFarPlane, farPlane);
 	}
 
+	public void setTestParam(float farPlane) {
+		GL20.glUniform1f(testParam, farPlane);
+	}
+
+	public void setCameraPos(Vector3d pos) {
+		GL20.glUniform3f(uCameraPos, (float) pos.x, (float) pos.y, (float) pos.z);
+	}
+
 	public void clear() {
 		filters.clear();
 	}

src/main/resources/assets/create/flywheel/shaders/area_effect.frag

@@ -12,6 +12,12 @@ uniform sampler2D uDepth;
 uniform sampler2D uColor;
 uniform float uNearPlane = 0.15;
 uniform float uFarPlane = 1.;
+uniform vec3 uCameraPos;
+
+uniform float testParam = 2.0;
+
+uniform mat4 uInverseProjection;
+uniform mat4 uInverseView;
 
 struct SphereFilter {
     vec4 sphere;// <vec3 position, float radius>
@@ -26,8 +32,9 @@ layout (std140) uniform Filters {
 };
 
 float linearizeDepth(float d, float zNear, float zFar) {
-    float z_n = 2.0 * d - 1.0;
+    float clipZ = 2.0 * d - 1.0;
-    return 2.0 * zNear * zFar / (zFar + zNear - z_n * (zFar - zNear));
+    float linearized = zNear * zFar / (zFar + zNear - clipZ * (zFar - zNear));
+    return testParam * linearized;
 }
 
 vec4 filterColor(mat4 colorOp, vec4 frag) {
@@ -41,7 +48,7 @@ float getDepth() {
     float depth = texture2D(uDepth, ScreenCoord).r;
 
     depth = linearizeDepth(depth, uNearPlane, uFarPlane);
-    //depth = ( - uNearPlane) / (uFarPlane - uNearPlane);
+    //depth = (depth - uNearPlane) / (uFarPlane - uNearPlane);
     //depth = depth / uFarPlane;
 
     return depth;
@@ -49,19 +56,24 @@ float getDepth() {
 
 void main() {
     float depth = getDepth();
-    vec3 worldPos = WorldDir * depth;
+    vec3 worldPos = WorldDir * depth - uCameraPos;
 
-    vec4 accum = texture2D(uColor, ScreenCoord);
+    vec4 diffuse = texture2D(uColor, ScreenCoord);
+    //
+    //    for (int i = 0; i < uCount; i++) {
+    //        SphereFilter s = uSpheres[i];
+    //
+    //        float distance = distance(s.sphere.xyz, worldPos);
+    //        float strength = 1 - smoothstep(s.sphere.w - s.feather, s.sphere.w + s.feather, distance);
+    //
+    //        accum = mix(accum, filterColor(s.colorOp, accum), strength);
+    //    }
+    //
+    //    Color = accum;
 
-    for (int i = 0; i < uCount; i++) {
+    vec3 fractionalCoords = fract(worldPos);
-        SphereFilter s = uSpheres[i];
 
-        float distance = distance(s.sphere.xyz, worldPos);
+    vec3 isBonudary = step(15./16., fractionalCoords);
-        float strength = 1 - smoothstep(s.sphere.w - s.feather, s.sphere.w + s.feather, distance);
 
-        accum = mix(accum, filterColor(s.colorOp, accum), strength);
+    Color = vec4(mix(diffuse.rgb, fractionalCoords, isBonudary), 1.);
-    }
-
-    Color = accum;
-    //Color = vec4(vec3(distance / uFarPlane), 1.);
 }