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our_gl.cpp
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our_gl.cpp
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#include <cmath>
#include <limits>
#include <cstdlib>
#include "our_gl.h"
Matrix ModelView;
Matrix Viewport;
Matrix Projection;
IShader::~IShader() {}
void viewport(int x, int y, int w, int h) {
Viewport = Matrix::identity();
Viewport[0][3] = x+w/2.f;
Viewport[1][3] = y+h/2.f;
Viewport[2][3] = 1.f;
Viewport[0][0] = w/2.f;
Viewport[1][1] = h/2.f;
Viewport[2][2] = 0;
}
void projection(float coeff) {
Projection = Matrix::identity();
Projection[3][2] = coeff;
}
void lookat(Vec3f eye, Vec3f center, Vec3f up) {
Vec3f z = (eye-center).normalize();
Vec3f x = cross(up,z).normalize();
Vec3f y = cross(z,x).normalize();
Matrix Minv = Matrix::identity();
Matrix Tr = Matrix::identity();
for (int i=0; i<3; i++) {
Minv[0][i] = x[i];
Minv[1][i] = y[i];
Minv[2][i] = z[i];
Tr[i][3] = -center[i];
}
ModelView = Minv*Tr;
}
Vec3f barycentric(Vec2f A, Vec2f B, Vec2f C, Vec2f P) {
Vec3f s[2];
for (int i=2; i--; ) {
s[i][0] = C[i]-A[i];
s[i][1] = B[i]-A[i];
s[i][2] = A[i]-P[i];
}
Vec3f u = cross(s[0], s[1]);
if (std::abs(u[2])>1e-2) // dont forget that u[2] is integer. If it is zero then triangle ABC is degenerate
return Vec3f(1.f-(u.x+u.y)/u.z, u.y/u.z, u.x/u.z);
return Vec3f(-1,1,1); // in this case generate negative coordinates, it will be thrown away by the rasterizator
}
void triangle(mat<4,3,float> &clipc, IShader &shader, TGAImage &image, float *zbuffer) {
mat<3,4,float> pts = (Viewport*clipc).transpose(); // transposed to ease access to each of the points
mat<3,2,float> pts2;
for (int i=0; i<3; i++) pts2[i] = proj<2>(pts[i]/pts[i][3]);
Vec2f bboxmin( std::numeric_limits<float>::max(), std::numeric_limits<float>::max());
Vec2f bboxmax(-std::numeric_limits<float>::max(), -std::numeric_limits<float>::max());
Vec2f clamp(image.get_width()-1, image.get_height()-1);
for (int i=0; i<3; i++) {
for (int j=0; j<2; j++) {
bboxmin[j] = std::max(0.f, std::min(bboxmin[j], pts2[i][j]));
bboxmax[j] = std::min(clamp[j], std::max(bboxmax[j], pts2[i][j]));
}
}
Vec2i P;
TGAColor color;
for (P.x=bboxmin.x; P.x<=bboxmax.x; P.x++) {
for (P.y=bboxmin.y; P.y<=bboxmax.y; P.y++) {
Vec3f bc_screen = barycentric(pts2[0], pts2[1], pts2[2], P);
Vec3f bc_clip = Vec3f(bc_screen.x/pts[0][3], bc_screen.y/pts[1][3], bc_screen.z/pts[2][3]);
bc_clip = bc_clip/(bc_clip.x+bc_clip.y+bc_clip.z);
float frag_depth = clipc[2]*bc_clip;
if (bc_screen.x<0 || bc_screen.y<0 || bc_screen.z<0 || zbuffer[P.x+P.y*image.get_width()]>frag_depth) continue;
bool discard = shader.fragment(bc_clip, color);
if (!discard) {
zbuffer[P.x+P.y*image.get_width()] = frag_depth;
image.set(P.x, P.y, color);
}
}
}
}