33-旋转三角形代码实现

application.cpp

void prepare() {
	texture = Image::createImage("assets/textures/test.jpg");

	p1.color = RGBA(255, 0, 0, 255);
	p1.uv = math::vec2f(0.0f, 0.0f);

	p2.color = RGBA(0, 255, 0, 255);
	p2.uv = math::vec2f(1.0f, 1.0f);

	p3.color = RGBA(0, 0, 255, 255);
	p3.uv = math::vec2f(1.0f, 0.0f);

	pos1 = {-1.5f, 0.0f, 0.0f, 1.0f};
	pos2 = {1.5f, 0.0f, 0.0f, 1.0f };
	pos3 = {0.0f, 2.0f, 0.0f, 1.0f };

	perspectiveMatrix = math::perspective(60.0f, (float)WIDTH / (float)HEIGHT, 0.1f, 100.0f);
	screenMatrix = math::screenMatrix<float>(WIDTH, HEIGHT);
}

float angle = 0.0f;
float cameraPos = 5.0f;
void Application::transform()
{
	angle += 0.01f;
	//cameraPos += 0.01f;

	//模型变换,旋转变换矩阵（先向上平移再旋转）
	modelMatrix = math::translate(math::mat4f(1.0f), math::vec3f{ 0.5f, 0.0f, 0.0f }) * math::rotate(math::mat4f(1.0f), angle, math::vec3f{ 0.0f, 1.0f, 0.0f });

	//模拟摄像机往后退
	auto cameraModelMatrix = math::translate(math::mat4f(1.0f), math::vec3f{ 0.0f, 0.0f, cameraPos });//一个单位Z轴平移矩阵（将相机从世界坐标系原点位移到指定位置）
	viewMatrix = math::inverse(cameraModelMatrix);//视图矩阵是相机模型矩阵的逆矩阵；逆矩阵：将相机坐标系位移到世界坐标系原点

	/*
	视图矩阵：将世界坐标转为相机坐标系中（视图矩阵的目的就是为了实现投影变换，两者的绑定的）
	*/

	//mvp矩阵相乘：将世界坐标系转为屏幕坐标系（得到的是四维的齐次坐标）
	auto sp1 = perspectiveMatrix * viewMatrix * modelMatrix * pos1;
	auto sp2 = perspectiveMatrix * viewMatrix * modelMatrix * pos2;
	auto sp3 = perspectiveMatrix * viewMatrix * modelMatrix * pos3;
    
	/*
	auto sp1 = viewMatrix * modelMatrix * pos1;
	auto sp2 = viewMatrix * modelMatrix * pos2;
	auto sp3 = viewMatrix * modelMatrix * pos3;
	*/

	//透视除法（此处故意设计z！=0）得到NDC坐标（除以w的目的就是为了从齐次坐标转为笛卡尔坐标）->（mvp变换得到的是齐次坐标）
	sp1 /= sp1.w;
	sp2 /= sp2.w;
	sp3 /= sp3.w;

	//屏幕空间变换，将NDC转为屏幕坐标
	sp1 = screenMatrix * sp1;
	sp2 = screenMatrix * sp2;
	sp3 = screenMatrix * sp3;

	mV0.x = sp1.x;
	mV0.y = sp1.y;

	mV1.x = sp2.x;
	mV1.y = sp2.y;

	mV2.x = sp3.x;
	mV2.y = sp3.y;
}