Haxel Engine learning 19-- Camera

完整代码：

https://github.com/DXT00/Hazel_study/tree/cc47879c0c24156514b93c9dcdcdc23cf46bc4ac/Hazel 

Camera属性：
position（x,y,z）,rotation(a1,a2,a3)

Field of view(FOV)

respect ratio

position,rotation : View matrix  -->the Inverse transform of the actual camera (view transform 和camera transform是相反的！比如 camera向左移，看到的Object就会向右移 OpenGL by itself is not familiar with the concept of a camera, but we can try to simulate one by moving all objects in the scene in the reverse direction, giving the illusion that we are moving. )

respect ratio : Projection matrix

 

所以最终像素点的位置 :  gl_Position = （Projection matrix * View matrix  * Model Matrix）* VertexPosition

Model Matrix : Object的转换矩阵

相机位置固定 --->Projection matrix * View matrix 固定 

Model Matrix --->每个Object不一样

---

Projection matrix * View matrix   ---> VP matrix

Projection matrix * View matrix  * Model Matrix  ---> MVP matrix

---

如果 VP * Model * vertex 写到shader里，那每个vertex都要乘一次

VP是个定值

 

可以这样：

把VP matrix 通过Uniform写入Shader

 

---

MyCode:

添加Camera类：

#pragma once
#include "glm/glm.hpp"
namespace Hazel {
	class OrthographicCamera
	{
	public:
		OrthographicCamera(){}
		OrthographicCamera(float left, float right, float bottom, float top);
	
		void SetPosition(const glm::vec3& position) { m_Position = position; }
		inline void SetViewMatrix(glm::mat4 view) { m_ViewMatix = view; }
		inline void SetProjectionMatrix(glm::mat4 projection) { m_ProjectionMatrix = projection; }
		inline const glm::mat4 &GetViewMatrix()const { return m_ViewMatix; };
		inline const glm::mat4 &GetProjectionMatrix()const { return m_ProjectionMatrix; };
	

		~OrthographicCamera();
		
	private:
		float m_zFar, m_zClose;
		float m_FOV;
		glm::vec3 m_Position;
		glm::mat4 m_ViewMatix;// is the inverse of the transformMatrix of the Camera!
		glm::mat4 m_ProjectionMatrix;
		glm::mat4 m_ViewProjectionMatrix;

		float m_Rotation = 0.0f;//rotate along z axis


	};

}

Shader中添加 view,projection,model矩阵

		const std::string vertexSrc = R"(
				#version 330 core
				
				layout(location = 0) in vec3 a_Position;
				layout(location = 1) in vec4 a_Color;

				out vec3 v_Position;
				out vec4 v_Color;

				uniform mat4 model;
				uniform mat4 view;
				uniform mat4 projection;

				void main()
				{
					v_Position = a_Position;
					v_Color = a_Color;
					gl_Position = projection*view*model*vec4(a_Position,1.0f);

				}


				)";
		const std::string fragmentSrc = R"(
				#version 330 core
				
				layout(location = 0) out vec4 color;
				layout(location = 1) out vec4 color1;

				in vec3 v_Position;
				in vec4 v_Color;
				
				void main()
				{

					color = v_Color;//vec4(v_Position*0.5+0.5, 1.0);

				}
				)";

渲染：

Application.cpp

void Application::Run()
	{
		while (m_Running)
		{
			
			RenderCommand::SetClearColor({ 0.1f, 0.1f, 0.1f, 1 });
			RenderCommand::Clear();
			Renderer::BeginScene();
			
			m_SquareShader->Bind();
			Renderer::Submit(m_SquareVA);

			m_Shader->Bind();
			glm::mat4 model = glm::mat4(1.0f); // make sure to initialize matrix to identity matrix first
			glm::mat4 view = glm::mat4(1.0f);
			glm::mat4 projection = glm::mat4(1.0f);
			model = glm::rotate(model, (float)glfwGetTime(), glm::vec3(0.5f, 1.0f, 0.0f));
			view = glm::translate(view, glm::vec3(0.0f, 0.0f, -3.0f));
			projection = glm::perspective(glm::radians(45.0f), (float)m_Window->GetWidth() / (float)m_Window->GetHeight(), 0.1f, 100.0f);
			m_Shader->setUniformMat4("view", view);
			m_Shader->setUniformMat4("projection", projection);
			m_Shader->setUniformMat4("model", model);
			Renderer::Submit(m_VertexArray);

			

			Renderer::EndScene();

			for (Layer* layer : m_LayerStack)
				layer->OnUpdate();

			m_ImGuiLayer->Begin();
			for (Layer* layer : m_LayerStack)
				layer->OnImGuiRender();
			m_ImGuiLayer->End();

			m_Window->OnUpdate();
		}
	}

Shader.cpp添加SetUniform：

	uint32_t Shader::GetUniformLocation(const std::string& name) const
	{
		return glGetUniformLocation(m_RendererID, name.c_str());
	}
	void Shader::setUniformMat4(const std::string &name, const glm::mat4 &mat) const
	{
		glUniformMatrix4fv(GetUniformLocation(name), 1, GL_FALSE, &mat[0][0]);
	}
}

F5运行，可以看到三角形绕轴 vec3(0.5f, 1.0f, 0.0f)旋转