Lesson05: Multi-Colored Cube

In this post we will try to draw a multi colored cube as shown above. The cube looks elongated because aspect ratio is not applied.

Implementation

MultiColorCube class is implemented as below to draw the single colored cube. 

 It's located in VOGLLib\Geometry\Cube\MultiColorCube.h.

       
//Implements multi colored cube 
class MultiColoredCube :public BaseGeometry
{
public:
	//OpenGL initialization
	void Init()
	{
		//initialize opengl context
		BaseGeometry::Init(new CubeMesh());
		//generate vbo data
		kount = mesh->GenerateVerticesData(false, VAOUtil::POS | VAOUtil::CLR, vaoutl);
		//setup vertices
		vaoutl.SetupVBO(0, VAOUtil::POS);
		vaoutl.SetupVBO(1, VAOUtil::CLR);
		vaoutl.unbindVAO();
	}

	//override
	virtual string vertexShaderSource()
	{
		return R"(
		#version 330 core
		layout (location = 0) in vec3 vVertex;
		layout (location = 1) in vec3 vColor;
		out vec3 fcolor;

		uniform mat4 transform;

		void main()
		{
		   gl_Position =  transform * vec4(vVertex, 1.0);
		   fcolor = vColor;
		};
		)";
	}

	//override
	virtual string fragmentShaderSource()
	{
		return R"(
		#version 330 core
		in vec3 fcolor;
		out vec4 FragColor;
		void main()
		{
		   FragColor = vec4(fcolor,1.0);
		};
		)";
	}
};
 

Lesson05 Project

This purpose of this Lesson05 project is to create a Window initialized with OpenGL context and draw a MultiColorCube with 6 colors one for each face.

As discussed in introduction create tutorial lesson project Lesson02 under Lessons folder.

Add a header file Scene.h as shown below. The class itself is self explanatory. 

The WM_CLOSE  event is  handled in OnCloseWindow function and the window is destroyed and  application is shutdown. 

The Init method calls BaseScene's Init to create hosting window and OpenGL Context. It also attaches BaseCameraInputHandler to rotate the cube either by keyboard or mouse inputs.

The DrawScene method draws the cube with multiple colors and rotates as per keyboard or mouse inputs.

The Cleanup method release the resources.

The Scene class is implemented as below. It's located in Lessons\Lesson05\Scene.h file.

       
#include "Scene\BaseScene.h"
#include "Geometry\Cube\MultiColoredCube.h"

class Scene:public BaseScene
{
public:
	//message handler
	BEGIN_MSG_MAP(Scene0)
		MESSAGE_HANDLER(WM_CLOSE, OnCloseWindow)
		CHAIN_MSG_MAP(BaseScene)
	END_MSG_MAP()

	//override
	int Init(RECT rect, WCHAR *windowname)
	{
		//create host window and context
		BaseScene::Init(rect, windowname);
		//attach mouse keyboard input handler
		mskbd = new BaseCameraInputHandler(m_hWnd);

		//Create multicolor cube
		cube.Init();
		
		return 0;
	}

	//release resources
	void Cleanup()
	{
		cube.Cleanup();
		delete mskbd;
		
	}
	
	//draw the scene
	void DrawScene()
	{
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
		//get model view projection matrix. 
		//only model is modified
		//view and projection will be identity matrix
		mskbd->fetchCameraData(&cube.camera);
		cube.Draw();

	}

	//Close the window
	LRESULT OnCloseWindow(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled)
	{
		bHandled = TRUE;
		DestroyWindow();
		PostQuitMessage(0);
		return 0;
	}


private:
	MultiColoredCube cube;
}; 
 

The main.cpp is located in Lessons\Lesson05\main.cpp file. It creates the scene object and calls its init method.

       
#include "Scene.h"

Scene scene;

int WINAPI WinMain(HINSTANCE inst, HINSTANCE prev, LPSTR cmd_line, int show)
{
	scene.Init(RECT{ 100, 100, 780, 500 }, L"Modern OpenGL-Tutorial - Lesson05");
	scene.ShowWindow(show);

	MSG msg;
	while (GetMessage(&msg, 0, 0, 0)) 
	{
		TranslateMessage(&msg);
		DispatchMessageA(&msg);
	}

	return 0;
}     
 

The output looks as shown in the top. The cube is rotated by 20 degrees pitch and 20 degrees yaw. The camera position at the origin looking down on -Z axis or the back face of the cube.

To rotate the cube X,Y and Z keys can be used. They rotate respectively pitch, yaw and roll the cube  by 10 degrees.

In the next post we shall learn essential 3d Math.