feat: add drawline function, also fix M_PI function

src/cam.c

@@ -3,9 +3,13 @@
 
 #include <math.h>
 
+#ifndef M_PI // MSCV doesn't implement M_PI by default
+    #define M_PI 3.14159265358979323846
+#endif
+
 Mat4f_t perspCam(float fov, float asp, float near, float far)
 {
-    const float t = 1.f / tanf(fov * 0.5f * (M_PI/180.f));
+    const float t = 1.f / tanf(fov * 0.5f * (float)(M_PI/180.));
     const float fn = far - near;
     const float persp[16] = 
     {

src/draw.c

@@ -3,6 +3,7 @@
 #include <string.h>
 #include "draw.h"
 #include "math/vec4.h"
+#include "math.h"
 
 char* canvas; 
 
@@ -29,6 +30,39 @@ static char drawPixel(float zBuffer)
     else return '#';
 }
 
+void drawLine(Vec4f_t p0, Vec4f_t p1, int width, int height)
+{
+    int x0 = (int)roundf(p0.x);
+    int y0 = (int)roundf(p0.y);
+    int x1 = (int)roundf(p1.x);
+    int y1 = (int)roundf(p1.y);
+
+    int dx = abs(x1 - x0);
+    int dy = abs(y1 - y0);
+
+    int sx = x0 < x1 ? 1 : -1;
+    int sy = y0 < y1 ? 1 : -1;
+
+    int err = dx - dy;
+
+    int len = (int)sqrtf((x1-x0)*(x1-x0) + (y1-y0)*(y1-y0));
+    int step = 0;
+
+    while (1) {
+        float t = len == 0 ? 0.f : (float)step / (float)len;
+        Vec4f_t p = vec4f_lerp(p0, p1, t);
+        drawCanvas(p, width, height);
+
+        if (x0 == x1 && y0 == y1) break;
+
+        int e2 = 2*err;
+        if (e2 > -dy) { err -= dy; x0 += sx; }
+        if (e2 < dx)  { err += dx; y0 += sy; }
+
+        step++;
+    }
+}
+
 void drawCanvas(Vec4f_t p, int width, int height)
 {
     int x = (int)p.x;

src/draw.h

@@ -6,6 +6,7 @@
 void initCanvas(int width, int height);
 void editCanvas(int width, int height);
 void drawCanvas(Vec4f_t p, int width, int height);
+void drawLine(Vec4f_t p0, Vec4f_t p1, int width, int height);
 void renderCanvas(int width, int height);
 void freeCanvas(void);
 

src/main.c

@@ -10,19 +10,25 @@ int main(int argc, const char** argv)
     const float near = 0.1, far = 1000;
 
     const float aspect = width / height;
-
+    
-    // xyz = [-1; 1]
-    Vec4f_t vec = vec4f(0.f, 0.f, -1.f, 1.f);
     Mat4f_t proj = perspCam(fov, aspect, near, far);
 
-    Vec4f_t v_clip = mat4f_mul_vec4f(proj, vec);
+    // xyz = [-1; 1]
+    Vec4f_t vec0 = vec4f(0.f, 0.f, -1.f, 1.f);
+    Vec4f_t v_clip0 = mat4f_mul_vec4f(proj, vec0);
+    normCoord_r(&v_clip0);
+    viewport_r(&v_clip0, width, height);
 
-    normCoord_r(&v_clip);
+    Vec4f_t vec1 = vec4f(0.f, 0.6f, -1.f, 1.f);
-    viewport_r(&v_clip, width, height);
+    Vec4f_t v_clip1 = mat4f_mul_vec4f(proj, vec1);
+    normCoord_r(&v_clip1);
+    viewport_r(&v_clip1, width, height);
     
     initCanvas(width, height);
-    drawCanvas(v_clip, width, height);
+    // drawCanvas(v_clip, width, height);
+    drawLine(v_clip0, v_clip1, width, height);
     renderCanvas(width, height);
-    printf("%f", v_clip.z);
+
+    freeCanvas();
     return 0;
 }