improved normal map in biplanar mapping shader

data/cage/shader/functions/biplanar.glsl

@@ -1,67 +1,78 @@
 
+// https://iquilezles.org/articles/biplanar/
+
 struct Biplanar
 {
+	vec3 normal;
+	ivec3 a1; // dominant axis indices
+	ivec3 a2; // second axis indices
+	ivec3 a3; // least significant axis indices
 	vec2 uv1, uv2;
-	vec2 d1x, d2x;
-	vec2 d1y, d2y;
+	vec2 dx1, dx2;
+	vec2 dy1, dy2;
 	vec2 w;
-	float div;
 };
 
 Biplanar biplanarPrepare(vec3 p, vec3 n, float k)
 {
 	Biplanar bip;
+	bip.normal = n;
 	vec3 dpdx = dFdx(p);
 	vec3 dpdy = dFdy(p);
 	n = abs(n);
-	ivec3 ma = (n.x > n.y && n.x > n.z) ? ivec3(0, 1, 2) : (n.y > n.z) ? ivec3(1, 2, 0) : ivec3(2, 0, 1);
-	ivec3 mi = (n.x < n.y && n.x < n.z) ? ivec3(0, 1, 2) : (n.y < n.z) ? ivec3(1, 2, 0) : ivec3(2, 0, 1);
-	ivec3 me = ivec3(3) - mi - ma;
-	bip.uv1 = vec2(p[ma.y], p[ma.z]);
-	bip.uv2 = vec2(p[me.y], p[me.z]);
-	bip.d1x = vec2(dpdx[ma.y], dpdx[ma.z]);
-	bip.d2x = vec2(dpdx[me.y], dpdx[me.z]);
-	bip.d1y = vec2(dpdy[ma.y], dpdy[ma.z]);
-	bip.d2y = vec2(dpdy[me.y], dpdy[me.z]);
-	bip.w = vec2(n[ma.x], n[me.x]);
+	bip.a1 = (n.x > n.y && n.x > n.z) ? ivec3(0, 1, 2) : (n.y > n.z) ? ivec3(1, 2, 0) : ivec3(2, 0, 1);
+	bip.a3 = (n.x < n.y && n.x < n.z) ? ivec3(0, 1, 2) : (n.y < n.z) ? ivec3(1, 2, 0) : ivec3(2, 0, 1);
+	bip.a2 = ivec3(3) - bip.a3 - bip.a1;
+	bip.uv1 = vec2(p[bip.a1.y], p[bip.a1.z]);
+	bip.uv2 = vec2(p[bip.a2.y], p[bip.a2.z]);
+	bip.dx1 = vec2(dpdx[bip.a1.y], dpdx[bip.a1.z]);
+	bip.dx2 = vec2(dpdx[bip.a2.y], dpdx[bip.a2.z]);
+	bip.dy1 = vec2(dpdy[bip.a1.y], dpdy[bip.a1.z]);
+	bip.dy2 = vec2(dpdy[bip.a2.y], dpdy[bip.a2.z]);
+	bip.w = vec2(n[bip.a1.x], n[bip.a2.x]);
 	bip.w = saturate((bip.w - 0.5773) / (1 - 0.5773));
 	bip.w = pow(bip.w, vec2(k / 8));
-	bip.div = 1 / (bip.w.x + bip.w.y);
+	bip.w /= bip.w[0] + bip.w[1];
 	return bip;
 }
 
 vec4 biplanarSample(sampler2D sam, Biplanar bip)
 {
-	vec4 x = textureGrad(sam, bip.uv1, bip.d1x, bip.d1y);
-	vec4 y = textureGrad(sam, bip.uv2, bip.d2x, bip.d2y);
-	return (x * bip.w.x + y * bip.w.y) * bip.div;
+	vec4 v1 = textureGrad(sam, bip.uv1, bip.dx1, bip.dy1);
+	vec4 v2 = textureGrad(sam, bip.uv2, bip.dx2, bip.dy2);
+	return v1 * bip.w[0] + v2 * bip.w[1];
 }
 
 vec4 biplanarSample(sampler2DArray sam, Biplanar bip, float arrayIndex)
 {
-	vec4 x = textureGrad(sam, vec3(bip.uv1, arrayIndex), bip.d1x, bip.d1y);
-	vec4 y = textureGrad(sam, vec3(bip.uv2, arrayIndex), bip.d2x, bip.d2y);
-	return (x * bip.w.x + y * bip.w.y) * bip.div;
+	vec4 v1 = textureGrad(sam, vec3(bip.uv1, arrayIndex), bip.dx1, bip.dy1);
+	vec4 v2 = textureGrad(sam, vec3(bip.uv2, arrayIndex), bip.dx2, bip.dy2);
+	return v1 * bip.w[0] + v2 * bip.w[1];
+}
+
+vec3 egacBiplanarNormal(Biplanar bip, vec3 n1, vec3 n2)
+{
+	// https://bgolus.medium.com/normal-mapping-for-a-triplanar-shader-10bf39dca05a
+	// whiteout blend
+	n1.x *= -1;
+	n2.x *= -1;
+	n1 = vec3(n1.xy + vec2(bip.normal[bip.a1.z], bip.normal[bip.a1.y]), abs(n1.z) * bip.normal[bip.a1.x]);
+	n2 = vec3(n2.xy + vec2(bip.normal[bip.a2.z], bip.normal[bip.a2.y]), abs(n2.z) * bip.normal[bip.a2.x]);
+	n1 = vec3(n1[bip.a1.z], n1[bip.a1.y], n1[bip.a1.x]);
+	n2 = vec3(n2[bip.a2.z], n2[bip.a2.y], n2[bip.a2.x]);
+	return n1 * bip.w[0] + n2 * bip.w[1];
 }
 
-vec3 biplanarSampleNormal(sampler2D sam, Biplanar bip, vec3 normal)
+vec3 biplanarSampleNormal(sampler2D sam, Biplanar bip)
 {
-	vec3 n1 = restoreNormalMap(textureGrad(sam, bip.uv1, bip.d1x, bip.d1y));
-	vec3 n2 = restoreNormalMap(textureGrad(sam, bip.uv2, bip.d2x, bip.d2y));
-	mat3 tbn = makeTangentSpace(normal, varPosition - uniViewport.eyePos.xyz, bip.uv1);
-	n1 = tbn * n1;
-	tbn = makeTangentSpace(normal, varPosition - uniViewport.eyePos.xyz, bip.uv2);
-	n2 = tbn * n2;
-	return normalize(n1 * bip.w.x + n2 * bip.w.y);
+	vec3 n1 = restoreNormalMap(textureGrad(sam, bip.uv1, bip.dx1, bip.dy1));
+	vec3 n2 = restoreNormalMap(textureGrad(sam, bip.uv2, bip.dx2, bip.dy2));
+	return egacBiplanarNormal(bip, n1, n2);
 }
 
-vec3 biplanarSampleNormal(sampler2DArray sam, Biplanar bip, vec3 normal, float arrayIndex)
+vec3 biplanarSampleNormal(sampler2DArray sam, Biplanar bip, float arrayIndex)
 {
-	vec3 n1 = restoreNormalMap(textureGrad(sam, vec3(bip.uv1, arrayIndex), bip.d1x, bip.d1y));
-	vec3 n2 = restoreNormalMap(textureGrad(sam, vec3(bip.uv2, arrayIndex), bip.d2x, bip.d2y));
-	mat3 tbn = makeTangentSpace(normal, varPosition - uniViewport.eyePos.xyz, bip.uv1);
-	n1 = tbn * n1;
-	tbn = makeTangentSpace(normal, varPosition - uniViewport.eyePos.xyz, bip.uv2);
-	n2 = tbn * n2;
-	return normalize(n1 * bip.w.x + n2 * bip.w.y);
+	vec3 n1 = restoreNormalMap(textureGrad(sam, vec3(bip.uv1, arrayIndex), bip.dx1, bip.dy1));
+	vec3 n2 = restoreNormalMap(textureGrad(sam, vec3(bip.uv2, arrayIndex), bip.dx2, bip.dy2));
+	return egacBiplanarNormal(bip, n1, n2);
 }