197 lines
6.4 KiB
C++
197 lines
6.4 KiB
C++
#include "color.h"
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#include "engine.h"
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#include "geometry.h"
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#include "util.h"
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#include <cstdio>
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// MACROS
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#define DrawPixel(buffer, width, color, x, y)\
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{\
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buffer[width * y + x] = color;\
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}
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// STRUCTURES
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struct BoundingBox
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{
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BoundingBox(Point &v0, Point &v1, Point &v2)
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{
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yMin = MIN(v0.y, MIN(v1.y, v2.y));
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yMax = MAX(v0.y, MAX(v1.y, v2.y));
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xMin = MIN(v0.x, MIN(v1.x, v2.x));
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xMax = MAX(v0.x, MAX(v1.x, v2.x));
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}
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float yMin, yMax;
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float xMin, xMax;
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};
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// PUBLIC FUNCTIONS
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void CullBackfaces(
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Mesh_LocalData &local, Mesh_TransformedData &transformed,
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Point &camPosition)
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{
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transformed.faces.clear();
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for (size_t f = 0; f < local.faces.size(); ++f)
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{
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unsigned int v0 = local.faces[f].vertIndex[0];
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unsigned int v1 = local.faces[f].vertIndex[1];
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unsigned int v2 = local.faces[f].vertIndex[2];
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Vector v01 = transformed.verts[v1].point - transformed.verts[v0].point;
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Vector v02 = transformed.verts[v2].point - transformed.verts[v0].point;
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Vector normal = Vector::Cross(v01, v02);
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// Store normal for flat shading
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local.faces[f].normal = normal;
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local.faces[f].normal.Normalize();
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// Invert for Blender-compatibility
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normal = -normal;
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// Eye vector to viewport
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Vector view = camPosition - transformed.verts[v0].point;
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float dot = Vector::Dot(normal, view);
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if (dot < EPSILON_E3)
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{
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transformed.faces.push_back(local.faces[f]);
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}
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}
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}
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void RenderMesh(Engine_Buffer &buffer, Mesh_TransformedData &mesh, bool smooth, Texture &texture,
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std::vector<TextureCoord> &uvs)
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{
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for(size_t f = 0; f < mesh.faces.size(); ++f)
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{
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// The vertices of this face
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unsigned int vIndex0 = mesh.faces[f].vertIndex[0];
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unsigned int vIndex1 = mesh.faces[f].vertIndex[1];
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unsigned int vIndex2 = mesh.faces[f].vertIndex[2];
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Vertex &v0 = mesh.verts[vIndex0];
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Vertex &v1 = mesh.verts[vIndex1];
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Vertex &v2 = mesh.verts[vIndex2];
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// The UVs of this face's vertices
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unsigned int tIndex0 = mesh.faces[f].textureIndex[0];
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unsigned int tIndex1 = mesh.faces[f].textureIndex[1];
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unsigned int tIndex2 = mesh.faces[f].textureIndex[2];
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TextureCoord &t0 = uvs[tIndex0];
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TextureCoord &t1 = uvs[tIndex1];
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TextureCoord &t2 = uvs[tIndex2];
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// Bounding box for barycentric calculations (top-left fill convention)
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BoundingBox box(v0.point, v1.point, v2.point);
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int yMin = (int)ceilf(box.yMin);
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int yMax = (int)ceilf(box.yMax) - 1;
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int xMin = (int)ceilf(box.xMin);
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int xMax = (int)ceilf(box.xMax) - 1;
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// Constants for this triangle used for barycentric calculations
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Vector v01 = v1.point - v0.point;
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Vector v02 = v2.point - v0.point;
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float dot0101 = Vector::Dot(v01, v01);
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float dot0102 = Vector::Dot(v01, v02);
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float dot0202 = Vector::Dot(v02, v02);
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// Iterate over the bounding box and determine if each point is in the triangle
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for (int y = yMin; y <= yMax; ++y)
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{
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for (int x = xMin; x <= xMax; ++x)
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{
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// Constant terms used for barycentric calculation
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Point p(x, y, 1.0f);
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Vector v0P = p - v0.point;
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float dot0P01 = Vector::Dot(v0P, v01);
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float dot0P02 = Vector::Dot(v0P, v02);
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float denomInv = 1.0f / ((dot0101 * dot0202) - (dot0102 * dot0102));
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// Calculate the barycentric coordinate of this point
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float barycenter[3];
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barycenter[1] = (dot0202 * dot0P01 - dot0102 * dot0P02) * denomInv;
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barycenter[2] = (dot0101 * dot0P02 - dot0102 * dot0P01) * denomInv;
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barycenter[0] = 1.0f - barycenter[1] - barycenter[2];
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// Point is inside the triangle
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if ( (barycenter[0] >= 0.0f)
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&& (barycenter[1] >= 0.0f)
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&& (barycenter[2] >= 0.0f))
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{
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// Constant terms used in the U and V interpolation
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float a = barycenter[0] * v1.point.w * v2.point.w;
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float b = barycenter[1] * v0.point.w * v2.point.w;
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float c = barycenter[2] * v0.point.w * v1.point.w;
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float abc = 1.0f / (a + b + c);
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// Interpolate U and V
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float u = ((a * t0.u) + (b * t1.u) + (c * t2.u)) * abc;
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float v = ((a * t0.v) + (b * t1.v) + (c * t2.v)) * abc;
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// Convert U and V to pixels in the texture image
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unsigned int uPixel = (unsigned int)(u * texture.width);
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unsigned int vPixel = (unsigned int)(v * texture.height);
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ColorF32 shading;
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// Gouraud shading - interpolate color based on vertices
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if (smooth)
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{
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shading =
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(barycenter[0] * v0.color)
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+ (barycenter[1] * v1.color)
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+ (barycenter[2] * v2.color);
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}
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// Flat shading - base color on single face color
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else
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{
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shading = mesh.faces[f].color;
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}
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// Shade the texel with lighting calculations
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ColorU32 texel = texture.texels[vPixel][uPixel];
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texel.r *= shading.r;
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texel.g *= shading.g;
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texel.b *= shading.b;
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// Interpolate 1/z for the z-buffer
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float zInv =
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1.0f /
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((barycenter[0] * v0.point.w)
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+ (barycenter[1] * v1.point.w)
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+ (barycenter[2] * v2.point.w));
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// Draw the pixel if it's closer than what's in the z-buffer
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int pixel = (y * buffer.width + x);
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if (zInv > buffer.zbuffer[pixel])
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{
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DrawPixel(buffer.buffer, buffer.width, texel.u32, x, y);
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buffer.zbuffer[pixel] = zInv;
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}
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}
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}
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}
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}
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}
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