wireframe rendering

Author: ssloy

geometry.h

@@ -0,0 +1,55 @@
+#ifndef __GEOMETRY_H__
+#define __GEOMETRY_H__
+
+#include <cmath>
+
+///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+template <class t> struct Vec2 {
+	union {
+		struct {t u, v;};
+		struct {t x, y;};
+		t raw[2];
+	};
+	Vec2() : u(0), v(0) {}
+	Vec2(t _u, t _v) : u(_u),v(_v) {}
+	inline Vec2<t> operator +(const Vec2<t> &V) const { return Vec2<t>(u+V.u, v+V.v); }
+	inline Vec2<t> operator -(const Vec2<t> &V) const { return Vec2<t>(u-V.u, v-V.v); }
+	inline Vec2<t> operator *(float f)          const { return Vec2<t>(u*f, v*f); }
+	template <class > friend std::ostream& operator<<(std::ostream& s, Vec2<t>& v);
+};
+
+template <class t> struct Vec3 {
+	union {
+		struct {t x, y, z;};
+		struct { t ivert, iuv, inorm; };
+		t raw[3];
+	};
+	Vec3() : x(0), y(0), z(0) {}
+	Vec3(t _x, t _y, t _z) : x(_x),y(_y),z(_z) {}
+	inline Vec3<t> operator ^(const Vec3<t> &v) const { return Vec3<t>(y*v.z-z*v.y, z*v.x-x*v.z, x*v.y-y*v.x); }
+	inline Vec3<t> operator +(const Vec3<t> &v) const { return Vec3<t>(x+v.x, y+v.y, z+v.z); }
+	inline Vec3<t> operator -(const Vec3<t> &v) const { return Vec3<t>(x-v.x, y-v.y, z-v.z); }
+	inline Vec3<t> operator *(float f)          const { return Vec3<t>(x*f, y*f, z*f); }
+	inline t       operator *(const Vec3<t> &v) const { return x*v.x + y*v.y + z*v.z; }
+	float norm () const { return std::sqrt(x*x+y*y+z*z); }
+	Vec3<t> & normalize(t l=1) { *this = (*this)*(l/norm()); return *this; }
+	template <class > friend std::ostream& operator<<(std::ostream& s, Vec3<t>& v);
+};
+
+typedef Vec2<float> Vec2f;
+typedef Vec2<int>   Vec2i;
+typedef Vec3<float> Vec3f;
+typedef Vec3<int>   Vec3i;
+
+template <class t> std::ostream& operator<<(std::ostream& s, Vec2<t>& v) {
+	s << "(" << v.x << ", " << v.y << ")\n";
+	return s;
+}
+
+template <class t> std::ostream& operator<<(std::ostream& s, Vec3<t>& v) {
+	s << "(" << v.x << ", " << v.y << ", " << v.z << ")\n";
+	return s;
+}
+
+#endif //__GEOMETRY_H__

main.cpp

@@ -1,8 +1,14 @@
+#include <vector>
 #include <cmath>
 #include "tgaimage.h"
+#include "model.h"
+#include "geometry.h"
 
 const TGAColor white = TGAColor(255, 255, 255, 255);
 const TGAColor red   = TGAColor(255, 0,   0,   255);
+Model *model = NULL;
+const int width  = 800;
+const int height = 800;
 
 void line(int x0, int y0, int x1, int y1, TGAImage &image, TGAColor color) {
     bool steep = false;
@@ -15,35 +21,42 @@ void line(int x0, int y0, int x1, int y1, TGAImage &image, TGAColor color) {
         std::swap(x0, x1);
         std::swap(y0, y1);
     }
-    int dx = x1-x0;
-    int dy = y1-y0;
-    int derror2 = std::abs(dy)*2;
-    int error2 = 0;
-    int y = y0;
+
     for (int x=x0; x<=x1; x++) {
+        float t = (x-x0)/(float)(x1-x0);
+        int y = y0*(1.-t) + y1*t;
         if (steep) {
-            image.set(y, x, TGAColor(255, 1));
+            image.set(y, x, color);
         } else {
-            image.set(x, y, TGAColor(255, 1));
-        }
-        error2 += derror2;
-
-        if (error2>dx) {
-            y += (y1>y0?1:-1);
-            error2 -= dx*2;
+            image.set(x, y, color);
         }
     }
 }
 
 int main(int argc, char** argv) {
-    TGAImage image(100, 100, TGAImage::RGB);
-    for (int i=0; i<1000000; i++) {
-        line(13, 20, 80, 40, image, white);
-        line(20, 13, 40, 80, image, red);
-        line(80, 40, 13, 20, image, red);
+    if (2==argc) {
+        model = new Model(argv[1]);
+    } else {
+        model = new Model("obj/african_head.obj");
     }
+
+    TGAImage image(width, height, TGAImage::RGB);
+    for (int i=0; i<model->nfaces(); i++) {
+        std::vector<int> face = model->face(i);
+        for (int j=0; j<3; j++) {
+            Vec3f v0 = model->vert(face[j]);
+            Vec3f v1 = model->vert(face[(j+1)%3]);
+            int x0 = (v0.x+1.)*width/2.;
+            int y0 = (v0.y+1.)*height/2.;
+            int x1 = (v1.x+1.)*width/2.;
+            int y1 = (v1.y+1.)*height/2.;
+            line(x0, y0, x1, y1, image, white);
+        }
+    }
+
     image.flip_vertically(); // i want to have the origin at the left bottom corner of the image
     image.write_tga_file("output.tga");
+    delete model;
     return 0;
 }
 

model.cpp

@@ -0,0 +1,54 @@
+#include <iostream>
+#include <string>
+#include <fstream>
+#include <sstream>
+#include <vector>
+#include "model.h"
+
+Model::Model(const char *filename) : verts_(), faces_() {
+    std::ifstream in;
+    in.open (filename, std::ifstream::in);
+    if (in.fail()) return;
+    std::string line;
+    while (!in.eof()) {
+        std::getline(in, line);
+        std::istringstream iss(line.c_str());
+        char trash;
+        if (!line.compare(0, 2, "v ")) {
+            iss >> trash;
+            Vec3f v;
+            for (int i=0;i<3;i++) iss >> v.raw[i];
+            verts_.push_back(v);
+        } else if (!line.compare(0, 2, "f ")) {
+            std::vector<int> f;
+            int itrash, idx;
+            iss >> trash;
+            while (iss >> idx >> trash >> itrash >> trash >> itrash) {
+                idx--; // in wavefront obj all indices start at 1, not zero
+                f.push_back(idx);
+            }
+            faces_.push_back(f);
+        }
+    }
+    std::cerr << "# v# " << verts_.size() << " f# "  << faces_.size() << std::endl;
+}
+
+Model::~Model() {
+}
+
+int Model::nverts() {
+    return (int)verts_.size();
+}
+
+int Model::nfaces() {
+    return (int)faces_.size();
+}
+
+std::vector<int> Model::face(int idx) {
+    return faces_[idx];
+}
+
+Vec3f Model::vert(int i) {
+    return verts_[i];
+}
+

model.h

@@ -0,0 +1,20 @@
+#ifndef __MODEL_H__
+#define __MODEL_H__
+
+#include <vector>
+#include "geometry.h"
+
+class Model {
+private:
+	std::vector<Vec3f> verts_;
+	std::vector<std::vector<int> > faces_;
+public:
+	Model(const char *filename);
+	~Model();
+	int nverts();
+	int nfaces();
+	Vec3f vert(int i);
+	std::vector<int> face(int idx);
+};
+
+#endif //__MODEL_H__