Switch to non-branching approach for GetMajorAxes

2026-03-28 21:27:46 +08:00
parent f620a650aa
commit 48a0e3facb
4 changed files with 62 additions and 58 deletions
@@ -0,0 +1,8 @@
+fileFormatVersion: 2
+guid: bb92af38d2a022242b4dddcb954f789e
+folderAsset: yes
+DefaultImporter:
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 
@@ -0,0 +1,54 @@
+#define EPSILON 0.0004f
+
+float CrossProduct(float2 A, float2 B)
+{
+    return A.x * B.y - A.y * B.x;
+}
+
+float SweepArea(float2 A, float2 B)
+{
+    return abs(CrossProduct(A, B));
+}
+
+float4x4 GetMajorAxes(float4x4 Axes, float4x4 AxesProjections)
+{
+    float4x4 result = (float4x4)0;
+
+    float2 x_proj = AxesProjections[0].xy;
+    float2 y_proj = AxesProjections[1].xy;
+    float2 z_proj = AxesProjections[2].xy;
+
+    float3 x_axes = Axes[0].xyz;
+    float3 y_axes = Axes[1].xyz;
+    float3 z_axes = Axes[2].xyz;
+
+    float xy_area = SweepArea(x_proj, y_proj);
+    float xz_area = SweepArea(x_proj, z_proj);
+    float yz_area = SweepArea(y_proj, z_proj);
+
+    // Compute selection weights using step
+    float xy_is_max = step(xz_area, xy_area) * step(yz_area, xy_area);
+    float xz_is_max = step(yz_area, xz_area) * (1.0 - xy_is_max);
+    float yz_is_max = 1.0 - xy_is_max - xz_is_max;
+
+    // Select axis0
+    float3 axis0 = 
+        xy_is_max * x_axes +
+        xz_is_max * x_axes +
+        yz_is_max * y_axes;
+
+    // Select axis1
+    float3 axis1 = 
+        xy_is_max * y_axes +
+        xz_is_max * z_axes +
+        yz_is_max * z_axes;
+
+    // Normalize and scale if length is below threshold
+    float len0 = length(axis0);
+    float len1 = length(axis1);
+    
+    result[0].xyz = normalize(axis0) * max(len0, EPSILON);
+    result[1].xyz = normalize(axis1) * max(len1, EPSILON);
+
+    return result;
+}
@@ -1,58 +0,0 @@
-#define EPSILON 0.0004f
-
-/// Hidden
-float CrossProduct(float2 A, float2 B)
-{
-    return A.x * B.y - A.y * B.x;
-}
-
-/// Hidden
-float SweepArea(float2 A, float2 B)
-{
-    return abs(CrossProduct(A, B));
-}
-
-float4x4 GetMajorAxes(float4x4 Axes, float4x4 AxesProjections)
-{
-    float4x4 result = (float4x4)0;
-
-    float2 x_proj = AxesProjections[0].xy;
-    float2 y_proj = AxesProjections[1].xy;
-    float2 z_proj = AxesProjections[2].xy;
-
-    float3 x_axes = Axes[0].xyz;
-    float3 y_axes = Axes[1].xyz;
-    float3 z_axes = Axes[2].xyz;
-
-    float xy_area = SweepArea(x_proj, y_proj);
-    float xz_area = SweepArea(x_proj, z_proj);
-    float yz_area = SweepArea(y_proj, z_proj);
-
-    if (xy_area > xz_area && xy_area > yz_area)
-    {
-        result[0].xyz = x_axes;
-        result[1].xyz = y_axes;
-    }
-    else if (xz_area > yz_area)
-    {
-        result[0].xyz = x_axes;
-        result[1].xyz = z_axes;
-    }
-    else
-    {
-        result[0].xyz = y_axes;
-        result[1].xyz = z_axes;
-    }
-
-    if (length(result[0].xyz) < 0.0004)
-    {
-        result[0].xyz = normalize(result[0].xyz) * EPSILON;
-    }
-        
-    if (length(result[1].xyz) < 0.0004)
-    {
-        result[1].xyz = normalize(result[1].xyz) * EPSILON;
-    }
-        
-    return result;
-}