From f1733b42a54e580f58c00b20eb78b2d084634f6c Mon Sep 17 00:00:00 2001
From: Austin Morlan <mail@austinmorlan.com>
Date: Tue, 18 Sep 2018 19:59:16 -0700
Subject: [PATCH] Clean up main render loop

---
 src/geometry.cpp | 55 ++++++++++++++++++++++--------------------------
 1 file changed, 25 insertions(+), 30 deletions(-)

diff --git a/src/geometry.cpp b/src/geometry.cpp
index e635196..a1fbc64 100644
--- a/src/geometry.cpp
+++ b/src/geometry.cpp
@@ -110,15 +110,12 @@ void RenderMesh(
         {
             for (int x = xMin; x <= xMax; ++x)
             {
-                // Constant terms used for barycentric calculation
+                // Calculate the barycentric coordinate of this point
                 Point p(x, y, 1.0f);
                 Vector v0P = p - p0;
                 float dot0P01 = Vector::Dot(v0P, v01);
                 float dot0P02 = Vector::Dot(v0P, v02);
                 float denomInv = 1.0f / ((dot0101 * dot0202) - (dot0102 * dot0102));
-
-
-                // Calculate the barycentric coordinate of this point
                 float barycenter[3];
                 barycenter[1] = (dot0202 * dot0P01 - dot0102 * dot0P02) * denomInv;
                 barycenter[2] = (dot0101 * dot0P02 - dot0102 * dot0P01) * denomInv;
@@ -130,47 +127,36 @@ void RenderMesh(
                         && (barycenter[1] >= 0.0f)
                         && (barycenter[2] >= 0.0f))
                 {
-                    ColorF32 &c0 = verts.data[face.vertIndex[0]].color;
-                    ColorF32 &c1 = verts.data[face.vertIndex[1]].color;
-                    ColorF32 &c2 = verts.data[face.vertIndex[2]].color;
+                    // Interpolate U and V of the texture for this point
+                    Texture &texture = textures.data[faces.data[f].materialIndex];
+                    UV &uv0 = uvs.data[face.uvIndex[0]];
+                    UV &uv1 = uvs.data[face.uvIndex[1]];
+                    UV &uv2 = uvs.data[face.uvIndex[2]];
 
-                    // Gouraud shading
-                    ColorF32 shading =
-                        (barycenter[0] * c0)
-                        + (barycenter[1] * c1)
-                        + (barycenter[2] * c2);
-
-
-                    // Constant terms used in the U and V interpolation
                     float a = barycenter[0] * p1.w * p2.w;
                     float b = barycenter[1] * p0.w * p2.w;
                     float c = barycenter[2] * p0.w * p1.w;
                     float abc = 1.0f / (a + b + c);
 
-                    UV &uv0 = uvs.data[face.uvIndex[0]];
-                    UV &uv1 = uvs.data[face.uvIndex[1]];
-                    UV &uv2 = uvs.data[face.uvIndex[2]];
+                    float uInterp =
+                        ((a * uv0.u) + (b * uv1.u) + (c * uv2.u))
+                        * abc
+                        * texture.width;
 
-                    // Interpolate U and V
-                    float uInterp = ((a * uv0.u) + (b * uv1.u) + (c * uv2.u)) * abc;
-                    float vInterp = ((a * uv0.v) + (b * uv1.v) + (c * uv2.v)) * abc;
+                    float vInterp =
+                        ((a * uv0.v) + (b * uv1.v) + (c * uv2.v))
+                        * abc
+                        * texture.height;
 
 
-                    // Convert U and V to pixels in the texture image
-                    Texture &texture = textures.data[faces.data[f].materialIndex];
-                    uInterp *= texture.width;
-                    vInterp *= texture.height;
+                    // Bilinear filtering
                     unsigned int u = (unsigned int)uInterp;
                     unsigned int v = (unsigned int)vInterp;
-
-                    // Constant terms for bilinear filtering
                     float du = uInterp - u;
                     float dv = vInterp - v;
                     float duDiff = 1 - du;
                     float dvDiff = 1 - dv;
 
-
-                    // Bilinear filtering
                     ColorU32 color;
                     color.b = (uint8_t)
                         (duDiff * dvDiff * texture.texels[v][u].b
@@ -191,7 +177,16 @@ void RenderMesh(
                          + duDiff * dv * texture.texels[v+1][u].r);
 
 
-                    // Shade the texture with the light calculations
+                    // Perform Gouraud shading on the texture
+                    ColorF32 &c0 = verts.data[face.vertIndex[0]].color;
+                    ColorF32 &c1 = verts.data[face.vertIndex[1]].color;
+                    ColorF32 &c2 = verts.data[face.vertIndex[2]].color;
+
+                    ColorF32 shading =
+                        (barycenter[0] * c0)
+                        + (barycenter[1] * c1)
+                        + (barycenter[2] * c2);
+
                     color.b *= shading.b;
                     color.g *= shading.g;
                     color.r *= shading.r;