Add perspective-correct texture mapping

include/geometry.h

@@ -14,9 +14,23 @@ struct Material
     ColorF32 kDiffuse;
 };
 
+struct Texture
+{
+    ColorU32 **texels;
+    unsigned int width;
+    unsigned int height;
+};
+
+struct TextureCoord
+{
+    float u;
+    float v;
+};
+
 struct Face
 {
     unsigned int vertIndex[3];
+    unsigned int textureIndex[3];
     Vector normal;
     ColorF32 color;
 };
@@ -32,6 +46,7 @@ struct Mesh_LocalData
 {
     std::vector<Vertex> verts;
     std::vector<Face> faces;
+    std::vector<TextureCoord> uvs;
 };
 
 struct Mesh_TransformedData
@@ -73,7 +88,8 @@ void CullBackfaces(
         Point &camPosition);
 
 void RenderMesh(
-        Engine_Buffer &buffer, Mesh_TransformedData &mesh, bool smooth);
+        Engine_Buffer &buffer, Mesh_TransformedData &mesh, bool smooth, Texture &texture,
+        std::vector<TextureCoord> &uvs);
 
 
 #define GEOMETRY_H

include/loader.h

@@ -4,6 +4,7 @@
 
 
 int LoadMesh(char *filename, Mesh &mesh);
+int LoadTexture(char *filename, Texture &texture);
 
 
 #define LOADER_H

src/engine.cpp

@@ -15,6 +15,7 @@
 static Mesh mesh;
 static Camera camera;
 static LightList lights;
+static Texture texture;
 
 
 // PRIVATE PROTOTYPES
@@ -129,10 +130,12 @@ void Engine_Render(Engine_Buffer &buffer, uint32_t input)
     for (size_t v = 0; v < mesh.transformed.verts.size(); ++v)
     {
         mesh.transformed.verts[v].point *= tView * tPersp * tScreen;
-        mesh.transformed.verts[v].point /= mesh.transformed.verts[v].point.w;
+        mesh.transformed.verts[v].point.x /= mesh.transformed.verts[v].point.w;
+        mesh.transformed.verts[v].point.y /= mesh.transformed.verts[v].point.w;
+        mesh.transformed.verts[v].point.z /= mesh.transformed.verts[v].point.w;
     }
 
-    RenderMesh(buffer, mesh.transformed, mesh.smooth);
+    RenderMesh(buffer, mesh.transformed, mesh.smooth, texture, mesh.local.uvs);
 }
 
 void Engine_Shutdown(void)

src/geometry.cpp

@@ -66,25 +66,37 @@ void CullBackfaces(
 
 }
 
-void RenderMesh(Engine_Buffer &buffer, Mesh_TransformedData &mesh, bool smooth)
+void RenderMesh(Engine_Buffer &buffer, Mesh_TransformedData &mesh, bool smooth, Texture &texture,
+        std::vector<TextureCoord> &uvs)
 {
     for(size_t f = 0; f < mesh.faces.size(); ++f)
     {
+        // The vertices of this face
         unsigned int vIndex0 = mesh.faces[f].vertIndex[0];
         unsigned int vIndex1 = mesh.faces[f].vertIndex[1];
         unsigned int vIndex2 = mesh.faces[f].vertIndex[2];
+        Vertex &v0 = mesh.verts[vIndex0];
+        Vertex &v1 = mesh.verts[vIndex1];
+        Vertex &v2 = mesh.verts[vIndex2];
 
-        Vertex v0 = mesh.verts[vIndex0];
-        Vertex v1 = mesh.verts[vIndex1];
-        Vertex v2 = mesh.verts[vIndex2];
 
-        // Bounding box used to for iterating over possible pixels of this triangle
+        // The UVs of this face's vertices
+        unsigned int tIndex0 = mesh.faces[f].textureIndex[0];
+        unsigned int tIndex1 = mesh.faces[f].textureIndex[1];
+        unsigned int tIndex2 = mesh.faces[f].textureIndex[2];
+        TextureCoord &t0 = uvs[tIndex0];
+        TextureCoord &t1 = uvs[tIndex1];
+        TextureCoord &t2 = uvs[tIndex2];
+
+
+        // Bounding box for barycentric calculations (top-left fill convention)
         BoundingBox box(v0.point, v1.point, v2.point);
         int yMin = (int)ceilf(box.yMin);
         int yMax = (int)ceilf(box.yMax) - 1;
         int xMin = (int)ceilf(box.xMin);
         int xMax = (int)ceilf(box.xMax) - 1;
 
+
         // Constants for this triangle used for barycentric calculations
         Vector v01 = v1.point - v0.point;
         Vector v02 = v2.point - v0.point;
@@ -92,57 +104,87 @@ void RenderMesh(Engine_Buffer &buffer, Mesh_TransformedData &mesh, bool smooth)
         float dot0102 = Vector::Dot(v01, v02);
         float dot0202 = Vector::Dot(v02, v02);
 
-        // Iterate bounding box and determine if each point is in the triangle
+
+        // Iterate over the bounding box and determine if each point is in the triangle
         for (int y = yMin; y <= yMax; ++y)
         {
             for (int x = xMin; x <= xMax; ++x)
             {
+                // Constant terms used for barycentric calculation
                 Point p(x, y, 1.0f);
-
                 Vector v0P = p - v0.point;
                 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;
                 barycenter[0] = 1.0f - barycenter[1] - barycenter[2];
 
+
                 // Point is inside the triangle
                 if ( (barycenter[0] >= 0.0f)
                     && (barycenter[1] >= 0.0f)
                     && (barycenter[2] >= 0.0f))
                 {
-                    ColorF32 totalColor;
+                    // Constant terms used in the U and V interpolation
+                    float a = barycenter[0] * v1.point.w * v2.point.w;
+                    float b = barycenter[1] * v0.point.w * v2.point.w;
+                    float c = barycenter[2] * v0.point.w * v1.point.w;
+                    float abc = 1.0f / (a + b + c);
 
+
+                    // Interpolate U and V
+                    float u = ((a * t0.u) + (b * t1.u) + (c * t2.u)) * abc;
+                    float v = ((a * t0.v) + (b * t1.v) + (c * t2.v)) * abc;
+
+
+                    // Convert U and V to pixels in the texture image
+                    unsigned int uPixel = (unsigned int)(u * texture.width);
+                    unsigned int vPixel = (unsigned int)(v * texture.height);
+
+
+                    ColorF32 shading;
+
+                    // Gouraud shading - interpolate color based on vertices
                     if (smooth)
                     {
-                        totalColor =
+                        shading =
                             (barycenter[0] * v0.color)
                             + (barycenter[1] * v1.color)
                             + (barycenter[2] * v2.color);
                     }
+                    // Flat shading - base color on single face color
                     else
                     {
-                        totalColor = mesh.faces[f].color;
+                        shading = mesh.faces[f].color;
                     }
 
-                    ColorU32 color = ColorF32::ConvertToU32(totalColor);
+
+                    // Shade the texel with lighting calculations
+                    ColorU32 texel = texture.texels[vPixel][uPixel];
+                    texel.r *= shading.r;
+                    texel.g *= shading.g;
+                    texel.b *= shading.b;
 
 
-                    float z =
+                    // Interpolate 1/z for the z-buffer
-                        (barycenter[0] * v0.point.z)
+                    float zInv =
-                        + (barycenter[1] * v1.point.z)
+                        1.0f /
-                        + (barycenter[2] * v2.point.z);
+                        ((barycenter[0] * v0.point.w)
+                        + (barycenter[1] * v1.point.w)
+                        + (barycenter[2] * v2.point.w));
 
-                    float zInv = 1.0f / z;
 
+
+                    // Draw the pixel if it's closer than what's in the z-buffer
                     int pixel = (y * buffer.width + x);
-
                     if (zInv > buffer.zbuffer[pixel])
                     {
-                        DrawPixel(buffer.buffer, buffer.width, color.u32, x, y);
+                        DrawPixel(buffer.buffer, buffer.width, texel.u32, x, y);
 
                         buffer.zbuffer[pixel] = zInv;
                     }

src/loader.cpp

@@ -1,6 +1,8 @@
 #include "loader.h"
 #include <cctype>
 #include <cstdio>
+#include <cstdint>
+#include <cstdlib>
 #include <cstring>
 
 
@@ -8,6 +10,28 @@
 static char *GetLine(char *buffer, int maxLength, FILE *fp);
 static void ComputeNormals(Mesh &mesh);
 
+#pragma pack(push, 1)
+struct BMP_Header
+{
+    uint16_t fileType;
+    uint32_t fileSize;
+    uint16_t reserved0;
+    uint16_t reserved1;
+    uint32_t bitmapOffset;
+    uint32_t size;
+    int32_t width;
+    int32_t height;
+    uint16_t planes;
+    uint16_t bitsPerPixel;
+    uint32_t compression;
+    uint32_t sizeOfBitmap;
+    int32_t horizRes;
+    int32_t vertRes;
+    uint32_t colorsUsed;
+    uint32_t colorsImportant;
+};
+#pragma pack(pop)
+
 
 // PUBLIC FUNCTIONS
 int LoadMesh(char *filename, Mesh &mesh)
@@ -31,6 +55,8 @@ int LoadMesh(char *filename, Mesh &mesh)
     while (token != NULL)
     {
         if (token[0] == 'v')
+        {
+            if (token[1] == ' ')
             {
                 Vertex v;
 
@@ -43,20 +69,39 @@ int LoadMesh(char *filename, Mesh &mesh)
 
                 mesh.local.verts.push_back(v);
             }
+            else if (token[1] == 't')
+            {
+                TextureCoord textureCoord;
+
+                sscanf(
+                        token, "%s %f %f",
+                        garbage,
+                        &textureCoord.u,
+                        &textureCoord.v);
+
+                mesh.local.uvs.push_back(textureCoord);
+            }
+        }
         else if (token[0] == 'f')
         {
             Face f;
 
-            sscanf(token, "%s %d %d %d",
+            sscanf(token, "%s %d/%d %d/%d %d/%d",
                     garbage,
                     &f.vertIndex[0],
+                    &f.textureIndex[0],
                     &f.vertIndex[1],
-                    &f.vertIndex[2]);
+                    &f.textureIndex[1],
+                    &f.vertIndex[2],
+                    &f.textureIndex[2]);
 
             // Convert to 0-indexed
             f.vertIndex[0] -= 1;
             f.vertIndex[1] -= 1;
             f.vertIndex[2] -= 1;
+            f.textureIndex[0] -= 1;
+            f.textureIndex[1] -= 1;
+            f.textureIndex[2] -= 1;
 
             mesh.local.faces.push_back(f);
         }
@@ -66,9 +111,7 @@ int LoadMesh(char *filename, Mesh &mesh)
 
     ComputeNormals(mesh);
 
-    printf("OBJ: %s\n", filename);
+    printf("Mesh: %s [v: %lu  f: %lu]\n", filename, mesh.local.verts.size(), mesh.local.faces.size());
-    printf("Verts: %lu\n", mesh.local.verts.size());
-    printf("Faces: %lu\n", mesh.local.faces.size());
 
     mesh.transformed.verts.resize(mesh.local.verts.size());
 
@@ -77,6 +120,53 @@ int LoadMesh(char *filename, Mesh &mesh)
     return 0;
 }
 
+int LoadTexture(char *filename, Texture &texture)
+{
+    FILE *fp = fopen(filename, "r");
+    if (fp == NULL)
+    {
+        fprintf(stderr, "Could not open file: %s\n", filename);
+        return -1;
+    }
+
+    BMP_Header header = {};
+    fread((void*)&header, sizeof(BMP_Header), 1, fp);
+    fseek(fp, header.bitmapOffset, SEEK_SET);
+
+    texture.texels = (ColorU32**)malloc((size_t)header.height * sizeof(ColorU32*));
+    for (int row = 0; row < header.height; ++row)
+    {
+        texture.texels[row] = (ColorU32*)calloc(1, (size_t)header.width * sizeof(ColorU32));
+    }
+
+    // Padding is added to image to align to 4-byte boundaries
+    size_t paddingSize = header.width % 4;
+    uint8_t *padding = (uint8_t*)malloc(paddingSize * sizeof(*padding));
+
+    for (int y = 0; y < header.height; ++y)
+    {
+        for (int x = 0; x < header.width; ++x)
+        {
+            fread(&texture.texels[y][x].b, 1, 1, fp);
+            fread(&texture.texels[y][x].g, 1, 1, fp);
+            fread(&texture.texels[y][x].r, 1, 1, fp);
+        }
+
+        // Discard padding byte
+        if (paddingSize != 0)
+        {
+            fread(padding, paddingSize, 1, fp);
+        }
+    }
+
+    texture.width = (unsigned int)header.width;
+    texture.height = (unsigned int)header.height;
+
+    fclose(fp);
+
+    return 0;
+}
+
 static char *GetLine(char *buffer, int maxLength, FILE *fp)
 {
     while(true)
@@ -86,8 +176,6 @@ static char *GetLine(char *buffer, int maxLength, FILE *fp)
             return NULL;
         }
 
-        // for (length = strlen(buffer), index = 0; isspace(buffer[index]); ++index);
-
         if (buffer[0] != 'v' && buffer[0] != 'f')
         {
             continue;