- 1综膀、能夠?qū)?shù)據(jù)一次性發(fā)送給GPU赁项，然后使用一個(gè)繪制函數(shù)讓OpenGL利用這些數(shù)據(jù)繪制多個(gè)物體葛躏，就會(huì)更方便了。這就是實(shí)例化
- 2悠菜、繪制個(gè)數(shù)并沒有上限舰攒，只是我的個(gè)數(shù)設(shè)置存在問題，我需要設(shè)置V3有400個(gè)悔醋，然后才能繪制出200個(gè)四邊形摩窃。 應(yīng)該是那個(gè)值設(shè)置錯(cuò)誤了。
- 3芬骄、綁定定點(diǎn)數(shù)組偶芍，上傳數(shù)據(jù)后，需要設(shè)置glVertexAttribDivisor(offLocation, 1);//第一個(gè)元素是屬性數(shù)組下標(biāo)m德玫，第二個(gè)元素時(shí)除數(shù)匪蟀，
隔多少個(gè)更新一次下標(biāo)。1代表繪制一個(gè)元素更新一次宰僧。
告訴OpenGL該什么時(shí)候更新定點(diǎn)屬性的內(nèi)容到新一數(shù)組材彪，第一個(gè)參數(shù)是定點(diǎn)屬性，第二個(gè)參數(shù)是屬性除數(shù)琴儿，默認(rèn)為0. - 4段化、實(shí)際繪制時(shí)調(diào)用，glDrawArraysInstanced(GL_TRIANGLES, 0, 6, 200); 最后一個(gè)參數(shù)造成，代表繪制實(shí)力的個(gè)數(shù)显熏，200個(gè)四邊形。
- 5晒屎、實(shí)例化數(shù)組喘蟆。
繪制多個(gè)四邊形案例：
//頂點(diǎn)著色器
attribute vec2 aPos;
attribute vec3 fragColor;
attribute vec3 offsets;
uniform mat4 projectionM;
uniform mat4 modelViewM;
varying lowp vec3 outTextCoord;
void main(){
outTextCoord = fragColor;
vec2 pos = aPos * (offsets.z/200.0);//z是通過數(shù)組傳遞進(jìn)來的
gl_Position = projectionM * modelViewM * vec4(pos.x+offsets.x,pos.y+offsets.y,0,1.0);
//gl_Position = projectionM * modelViewM * vec4(aPos.x+offsets.x,aPos.y+offsets.y,0,1.0);
//gl_Position = projectionM * modelViewM * vec4(aPos.x + gl_InstanceID*0.1,aPos.y*gl_InstanceID*0.1,0,1.0);
}
//加載VA0
- (GLuint)loadVAOAndVBO{
KSVec3 v3[400];
int index = 0;
float offset = 0.1f;
for (int y = -20; y < 20; y += 2)
{
for (int x = -10; x < 10; x += 1)
{
KSVec3 translation;
translation.x = (float)x / 10.0f + offset;
translation.y = (float)y / 10.0f + offset;
translation.z = index;
v3[index++] = translation;
}
}
//將數(shù)據(jù)上傳到著色器
GLuint offPInt;
glGenBuffers(1, &offPInt);
glBindBuffer(GL_ARRAY_BUFFER, offPInt);
glBufferData(GL_ARRAY_BUFFER, sizeof(v3), &v3[0], GL_DYNAMIC_DRAW);
GLuint VAO,VBO;
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBindVertexArray(VAO);
glBufferData(GL_ARRAY_BUFFER, sizeof(quadVertices), &quadVertices, GL_DYNAMIC_DRAW);
GLuint aposId = glGetAttribLocation(self.myProgram, "aPos");
GLuint textCoordId = glGetAttribLocation(self.myProgram, "fragColor");
glVertexAttribPointer(aposId, 2, GL_FLOAT, GL_FALSE, 5*sizeof(GLfloat), NULL);
glVertexAttribPointer(textCoordId, 3, GL_FLOAT, GL_FALSE, 5*sizeof(GLfloat), NULL+2*(sizeof(GLfloat)));
glEnableVertexAttribArray(aposId);
glEnableVertexAttribArray(textCoordId);
GLuint offLocation = glGetAttribLocation(self.myProgram, "offsets");
glBindBuffer(GL_ARRAY_BUFFER, offPInt);
glVertexAttribPointer(offLocation, 3, GL_FLOAT, GL_FALSE, 3*sizeof(CGFloat), NULL);
glEnableVertexAttribArray(offLocation);
glBindBuffer(GL_ARRAY_BUFFER, 0);
//設(shè)置除數(shù)，每次渲染一個(gè)實(shí)例更新一下該屬性鼓鲁，所以設(shè)置成1.
glVertexAttribDivisor(offLocation, 1);
return VAO;
}
// 渲染
- (void)render{
[ZKLodaShader glCheckError];
glEnable(GL_DEPTH_TEST);
glClearColor(0.5, 0.5, 0, 1);
glClearDepthf(1.0);
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
if (!self.myProgram) {
self.myProgram = [self loadShader];
}
if (self.myProgram) {
glUseProgram(self.myProgram);
} else {
NSLog(@"著色器程序?yàn)榭?-- ");
return ;
}
[ZKLodaShader glCheckError];
GLuint VAO = [self loadVAOAndVBO];
[ZKLodaShader glCheckError];
glViewport(0, 0, _viewWidth, _viewHeight);
//設(shè)置變換
GLuint projMId = glGetUniformLocation(self.myProgram, "projectionM");
GLuint modlMId = glGetUniformLocation(self.myProgram, "modelViewM");
KSMatrix4 projM,modelViewM;
ksMatrixLoadIdentity(&projM);
ksMatrixLoadIdentity(&modelViewM);
[ZKLodaShader glCheckError];
ksPerspective(&projM, 45, (_viewWidth*1.0)/(_viewHeight*1.0), 0.1, 100);
//ksOrtho(&projM, -1, 1, -1, 1, 0, 100);
glUniformMatrix4fv(projMId, 1, GL_FALSE, &projM.m[0][0]);
ksTranslate(&modelViewM, 0, 0, -5);
_angle += 2;
//ksRotate(&modelViewM, _angle, 1, 1, 0);
glUniformMatrix4fv(modlMId, 1, GL_FALSE, &modelViewM.m[0][0]);
[ZKLodaShader glCheckError];
//繪制
glBindVertexArray(VAO);
glDrawArraysInstanced(GL_TRIANGLES, 0, 6, 200);
glBindVertexArray(0);
glDeleteVertexArrays(1, &VAO);
[ZKLodaShader glCheckError];
if (_myColorRenderBuffer) {
glBindRenderbuffer(GL_RENDERBUFFER, _myColorRenderBuffer);
}
glBindVertexArray(0);
glDeleteVertexArrays(1, &VAO);
[self.myContext presentRenderbuffer:GL_RENDERBUFFER];
}
效果圖：
實(shí)例化渲染.png
小行星帶效果渲染：
這里還有點(diǎn)問題蕴轨，需要再調(diào)試一下。
