平面着色（Flat Shading）
平面着色指的是3D模型上每个多边形（通常是三角形）统一地着色。
平面着色编程
在light.h中新写一个类型结构体light_t内含一个三维向量表示平行光照方向。
typedef struct
{
vec3_t direction;
}light_t;
引用light.c中的light
extern light_t light;
声明光照强度方法
uint32_t light_apply_intensity(uint32_t original_color, float percentage_factor);
在light.c中定义光源方向为z轴方向
light_t light = {
.direction = { 0, 0, 1}
};
| 在light.c中写下计算光照强度的方法内容，通过分别计算r,g,b受光照影响后的参数再通过 | 符号组成一个32位的颜色值。 |
// Change color based on a percentage factor to represent light intensity
uint32_t light_apply_intensity(uint32_t original_color, float percentage_factor){
if (percentage_factor < 0) percentage_factor = 0;
if (percentage_factor > 1) percentage_factor = 1;
uint32_t a = (original_color & 0xFF000000);
uint32_t r = (original_color & 0x00FF0000) * percentage_factor;
uint32_t g = (original_color & 0x0000FF00) * percentage_factor;
uint32_t b = (original_color & 0x000000FF) * percentage_factor;
uint32_t new_color = a | (r & 0x00FF0000) | (g & 0x0000FF00) | (b & 0x000000FF);
return new_color;
}
计算法线点乘光方向的结果，再应用之前的函数混合物体本身的颜色。
// Calculate the shade intensity based on how aliged is the face normal and the light direction
float light_intensity_factor = -vec3_dot(normal, light.direction);
// Calculate the triangle color based on the light angle
uint32_t triangle_color = light_apply_intensity(mesh_face.color, light_intensity_factor);
翻转屏幕空间坐标
// invert the y values to account for flipped screen y coordinate
projected_points[j].y *= -1;
