【Game Engine】第二節：配置googleTest & 初步開發Vector2D

配置GoogleTest

採用TDD(Test-Driven-Development)方式開發引擎，使用GoogleTest進行程序測試，便於開發過程中發現錯誤。

GoogleTest

• 下載:Github

• 環境搭建

  • 拷貝googletest目錄中的src與include中gtest文件夾，放置於Middleware/gtest
  • 建立新項目engineTester，將gtest/src/gtest-all.cc添加至項目中（此cpp爲所有程序代碼的集合）
  • 添加myMain.cpp，編譯成功

• 使用方法

  • 新建MyTempTestFile.cpp，包含gtest/test.h

#include <gtest/gtest.h>

TEST(MyTestSuiteName, MyTestName) {
   int a = 1, b = 2, c = a + b;
   EXPECT_EQ(c, 3);
   EXPECT_TRUE(c == 3);
}

初步編寫Vector2D

• 初步實現加法，常數乘法

//Vector2D.h
namespace Math {
	struct Vector2D {
		float x;
		float y;
		explicit Vector2D(const float& x = 0.0f, const float& y = 0.0f) :x(x), y(y) {}
	};
	inline Vector2D operator + (const Vector2D& a, const Vector2D& b);
	inline Vector2D operator * (const Vector2D& a, const float& b);
	inline Vector2D operator * (const float& a, const Vector2D& b);

	#include "Vector2D.inl"
}

//Vector2D.inl
Vector2D operator + (const Vector2D& a, const Vector2D& b) {
	return Vector2D(a.x + b.x, a.y + b.y);
}
Vector2D operator * (const Vector2D & a, const float& b) {
	return Vector2D(a.x * b, a.y * b);
}
Vector2D operator *(const float& a, const Vector2D & b) {
	return Vector2D(a * b.x, a * b.y);
}

實現openGL多幀繪製

• QTimer && Q_OBJECT

  • QTimer主要實現設定時間或立即觸發某一個槽，這裏用來觸發myUpdate
  • connect(&myTimer,SIGNAL(timeout()),this,SLOT(myUpdate));
  • 這裏需要myUpdate是一個槽信號，所以需要加private slots:
  • 當對象需要信號槽時，需要令其爲Q_OBJECT，在類內添加Q_OBJECT宏
  • 此時還需要利用QT程序中的moc.exe對Q_OBJECT程序進行重新編譯
  • 查找到moc.exe後執行" moc.exe MyGlWindow.h > MyGlWindow_moc.cpp"到項目中
  • 最後編譯成功，循環繪製

#ifndef SANDBOX_MY_GL_WINDOW
#define SANDBOX_MY_GL_WINDOW
#include <QtOpenGL/qgl.h>
#include <QtCore/qtimer.h>

class MyGlWindow : public QGLWidget
{
	Q_OBJECT

	QTimer myTimer;

protected:
	void initializeGL();
	void paintGL();
	void resizeGL(int, int);
private slots:
	void myUpdate();
};

#endif

簡易的圖形移動

• glBufferData不傳遞verts內容，只開闢verts大小內存，並設置爲GL_DYNAMIC_DRAW
• 在每次繪製前對verts進行矢量位移，通過glBufferSubData傳遞修改後的verts
• update中設置移動速度，迭代位移矢量，重繪圖像

#include <GL/glew.h>
#include "MyGlWindow.h"
#include <cassert>
#include <Math/Vector2D.h>
using Math::Vector2D;
namespace {
	Vector2D verts[] = {
			Vector2D(+0.1f,-0.1f),
			Vector2D(+0.0f,+0.1f),
			Vector2D(-0.1f,-0.1f),
	};
	Vector2D shipPosition(0.0f, 0.0f);
	const int VERTS_NUM = sizeof(verts) / sizeof(*verts);
}

void MyGlWindow::initializeGL() {
	GLenum errorCode = glewInit();
	assert(errorCode == 0);
	GLuint myBufferID;
	glGenBuffers(1, &myBufferID);
	glBindBuffer(GL_ARRAY_BUFFER, myBufferID);
	
	glBufferData(GL_ARRAY_BUFFER, sizeof verts, NULL,
		GL_DYNAMIC_DRAW);

	connect(&myTimer, SIGNAL(timeout()), this, SLOT(myUpdate()));
	myTimer.start(0);
}

void MyGlWindow::paintGL() {
	glClear(GL_COLOR_BUFFER_BIT);
	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, 0);

	glBufferData(GL_ARRAY_BUFFER, sizeof verts, verts, GL_DYNAMIC_DRAW);

	Vector2D transVerts[VERTS_NUM];
	for (int i = 0; i < VERTS_NUM; i++)
		transVerts[i] = verts[i] + shipPosition;

	glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof transVerts, transVerts);

	glDrawArrays(GL_TRIANGLES, 0, 3);
}

void MyGlWindow::myUpdate() {
	Vector2D velocity(0.001f,0.001f);
	shipPosition = shipPosition + velocity;
	repaint();
}

void MyGlWindow::resizeGL(int w, int h) {
	glViewport(0, 0, w, h);
}

項目目錄