qt opengl 2d紋理到3d球面
阿新 • • 發佈：2018-12-12
根據前面的實踐，已能通過程式碼生成球面的頂點，要將2維圖貼到球表面；只要能計算出每個頂點對應的紋理座標就可以了；關於2維圖貼到球面的公式如下：
float pi = 3.14159265;
U = arcsin(z / R)/pi + 0.5;
V = arctan(y/x)/2/pi;
x、y、z分別為頂點的三個座標。由此我們便可以貼圖了，另外我們還可以利用shader函式幫我們計算，以減少cpu消耗。
我在貼圖的同時，加入了光照效果；其渲染器實現如下：
#ifndef BALLTEXTURERENDER_H #define BALLTEXTURERENDER_H #include <QOpenGLExtraFunctions> #include <QOpenGLTexture> #include <QOpenGLBuffer> #include <QOpenGLShaderProgram> #include <QImage> #define PI 3.14159265f class BallTextureRender { public: BallTextureRender() = default; ~BallTextureRender(); void initsize(float r,QImage &img); //根據圖片，生成紋理資料 void render(QOpenGLExtraFunctions *f,QMatrix4x4 &pMatrix,QMatrix4x4 &vMatrix,QMatrix4x4 &mMatrix,QVector3D &lightLocation,QVector3D &camera); //渲染 private: QOpenGLShaderProgram program_; QOpenGLTexture *texture_{nullptr}; QOpenGLBuffer vbo_; float r_ = 0.0f; QVector<GLfloat> points_; }; #endif // BALLTEXTURERENDER_H
#include "balltexturerender.h" BallTextureRender::~BallTextureRender() { if(texture_){ texture_->destroy(); delete texture_; } } void BallTextureRender::initsize(float r, QImage &img) { program_.addCacheableShaderFromSourceFile(QOpenGLShader::Vertex,"vsrc.vert"); program_.addCacheableShaderFromSourceFile(QOpenGLShader::Fragment,"fsrc.frag"); program_.link(); r_ = r; //生成球面頂點 int angleSpan = 10; //弧度 = 角度 * PI / 180 for(int vAngle = -90; vAngle < 90; vAngle = vAngle + angleSpan){ //生成球面頂點 for(int hAngle = 0; hAngle <= 360; hAngle = hAngle + angleSpan){ float x0 = r * ::cos(vAngle * PI / 180) * ::cos(hAngle * PI / 180); float y0 = r * ::cos(vAngle * PI / 180) * ::sin(hAngle * PI / 180); float z0 = r * ::sin(vAngle * PI / 180); float x1 = r * ::cos(vAngle * PI / 180) * ::cos((hAngle + angleSpan) * PI / 180); float y1 = r * ::cos(vAngle * PI / 180) * ::sin((hAngle + angleSpan) * PI / 180); float z1 = r * ::sin(vAngle * PI / 180); float x2 = r * ::cos((vAngle + angleSpan) * PI / 180) * ::cos((hAngle + angleSpan) * PI / 180); float y2 = r * ::cos((vAngle + angleSpan) * PI / 180) * ::sin((hAngle + angleSpan) * PI / 180); float z2 = r * ::sin((vAngle + angleSpan) * PI / 180); float x3 = r * ::cos((vAngle + angleSpan) * PI / 180) * ::cos(hAngle * PI / 180); float y3 = r * ::cos((vAngle + angleSpan) * PI / 180) * ::sin(hAngle * PI / 180); float z3 = r * ::sin((vAngle + angleSpan) * PI / 180); points_ << x1 << y1 << z1 << x3 << y3 << z3 << x0 << y0 << z0 << x1 << y1 << z1 << x2 << y2 << z2 << x3 << y3 << z3; } } texture_ = new QOpenGLTexture(img); //生成紋理資料 vbo_.create(); vbo_.bind(); vbo_.allocate(points_.constData(),points_.count() * sizeof GLfloat); } void BallTextureRender::render(QOpenGLExtraFunctions *f, QMatrix4x4 &pMatrix, QMatrix4x4 &vMatrix, QMatrix4x4 &mMatrix, QVector3D &lightLocation, QVector3D &camera) { f->glEnable(GL_DEPTH_TEST); f->glEnable(GL_CULL_FACE); program_.bind(); vbo_.bind(); f->glActiveTexture(GL_TEXTURE0 + 0); //使用0號紋理 program_.setUniformValue("uPMatrix",pMatrix); program_.setUniformValue("uVMatrix",vMatrix); program_.setUniformValue("uMMatrix",mMatrix); program_.setUniformValue("uLightLocation",lightLocation); program_.setUniformValue("uCamera",camera); program_.setUniformValue("uR",r_); program_.setUniformValue("sTexture",0); program_.enableAttributeArray(0); program_.enableAttributeArray(1); texture_->bind(0); //球面上的頂點，同時也是法向量 program_.setAttributeBuffer(0,GL_FLOAT,0,3,0); program_.setAttributeBuffer(1,GL_FLOAT,0,3,0); f->glDrawArrays(GL_TRIANGLES,0,points_.count() / 3); program_.disableAttributeArray(0); program_.disableAttributeArray(1); texture_->release(); vbo_.release(); program_.release(); f->glDisable(GL_DEPTH_TEST); f->glDisable(GL_CULL_FACE); }
其shader如下，光照部分採用的混合光，和前面的一樣。
#version 330 uniform mat4 uPMatrix,uVMatrix,uMMatrix; //投影，檢視，轉換矩陣 uniform vec3 uLightLocation,uCamera; //光源位置，攝像機位置 uniform float uR; //球半徑 layout (location = 0) in vec3 aPosition; layout (location = 1) in vec3 aNormal; smooth out vec2 vTextureCood; //每個頂點對應的紋理座標 smooth out vec4 vAmbient; //環境光強度，傳遞到片元著色器 smooth out vec4 vDiffuse; //散射光強度，傳遞到片元著色器 smooth out vec4 vSpecular; //調光強度，傳遞到片元著色器 void pointLight(in vec3 normal,inout vec4 ambient,inout vec4 diffuse,inout vec4 specular,in vec4 lightAmbient,in vec4 lightDiffuse,in vec4 lightSpecular,in float shininess){ ambient = lightAmbient; vec3 normalTarget = aPosition + normal; vec3 newNormal = normalize((uMMatrix * vec4(normalTarget,1)).xyz - (uMMatrix * vec4(aPosition,1)).xyz); vec3 eye = normalize(uCamera - (uMMatrix * vec4(aPosition,1)).xyz); vec3 vp = normalize(uLightLocation - (uMMatrix * vec4(aPosition,1)).xyz); vec3 halfVector = normalize(eye + vp); float nDotViewPotision = max(0.0,dot(newNormal,vp)); diffuse = lightDiffuse * nDotViewPotision; float nDotViewHalfVector = dot(newNormal,halfVector); float powerFactor = max(0.0,pow(nDotViewHalfVector,shininess)); specular = lightSpecular * powerFactor; } void main(void) { gl_Position = uPMatrix * uVMatrix * uMMatrix * vec4(aPosition,1); vec4 ambient = vec4(0.0,0.0,0.0,0.0),diffuse = vec4(0.0,0.0,0.0,0.0),specular = vec4(0.0,0.0,0.0,0.0); pointLight(aNormal,ambient,diffuse,specular,vec4(0.15,0.15,0.15,1.0),vec4(0.8,0.8,0.8,1.0),vec4(0.7,0.7,0.7,1),50); vec2 textureCood = vec2(0.0,0.0); float pi = 3.14159265; textureCood.x = asin(aPosition.z / uR)/pi + 0.5; //根據公式計算u座標 textureCood.y = atan(aPosition.y/aPosition.x)/2/pi; //根據公式計算v座標 vTextureCood = textureCood; vAmbient = ambient; vDiffuse = diffuse; vSpecular = specular; }
通過以上程式碼渲染器就完成了，接下來是使用。我讓球面在自轉的同時也執行了公轉。實現如下
#ifndef WIDGET_H
#define WIDGET_H
#include <QOpenGLWidget>
#include <QTimer>
#include "balltexturerender.h"
class Widget : public QOpenGLWidget
{
Q_OBJECT
public:
Widget(QWidget *parent = 0);
~Widget();
protected:
void initializeGL() override;
void paintGL() override;
void resizeGL(int w,int h) override;
private:
BallTextureRender render_; //渲染器
QVector3D lightLocation_,camera_; //光源位置和攝像機位置
QMatrix4x4 pMatrix; //投影矩陣
QTimer tm_;
float angle_ = 0; //旋轉角度
private slots:
void slotTimeout();
};
#endif // WIDGET_H
#include "widget.h"
Widget::Widget(QWidget *parent)
: QOpenGLWidget(parent)
{
connect(&tm_,SIGNAL(timeout()),this,SLOT(slotTimeout()));
tm_.start(30);
}
Widget::~Widget()
{
}
void Widget::initializeGL()
{
render_.initsize(1.0,QImage("test.jpg")); //生成頂點和紋理資料
lightLocation_ = QVector3D(50,10,0);
camera_ = QVector3D(0,0,6);
}
void Widget::paintGL()
{
QOpenGLExtraFunctions *f = QOpenGLContext::currentContext()->extraFunctions();
f->glClearColor(0.0,0.0,0.0,1.0);
f->glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
QMatrix4x4 vMatrix;
vMatrix.lookAt(camera_,QVector3D(0,0,-1),QVector3D(0,1,0));
QMatrix4x4 mMatrix;
//先x軸旋轉30度，然後再y軸旋轉一個遞增角度，最後平移，實現公轉和自轉
mMatrix.rotate(30,1,0,0);
mMatrix.rotate(angle_,0,1,0);
mMatrix.translate(1.5,0,0);
render_.render(f,pMatrix,vMatrix,mMatrix,lightLocation_,camera_);
angle_ += 5;
}
void Widget::resizeGL(int w, int h)
{
pMatrix.setToIdentity();
pMatrix.perspective(45,float(w)/h,0.01f,100.0f);
}
void Widget::slotTimeout()
{
update();
}
