我遇到了一个问题,我试图在一个glkviewcontroller中使用两个vbo。第一个存储三角形的顶点数据。第二个存储行数据。但是,当我尝试绑定第二个vbo时,代码停止绘制(或覆盖)第一个vbo中包含的场景-即仅绘制线条。
在我的draw方法中:
首先画三角形
glEnableVertexAttribArray(GLKVertexAttribPosition);
glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, Position));
glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, TexCoord));
glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _indexBuffer);
[self.effect prepareToDraw];
glClearColor(0.5, 0.5, 0.5, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
glDrawElements(GL_TRIANGLES, nLiveSquares*6, GL_UNSIGNED_SHORT, 0);
现在我要画线条
glDisable(GL_BLEND);
glDisable(GL_TEXTURE_2D);
glBindBuffer(GL_ARRAY_BUFFER, _lineBuffer);
glEnableVertexAttribArray(GLKVertexAttribPosition);
glVertexAttribPointer(GLKVertexAttribPosition,2,GL_FLOAT,GL_FALSE,2*4,0);
// Set the line width
glLineWidth(5.0);
// Render the line
glDrawArrays(GL_LINE_STRIP, 0, 2);
glEnable(GL_BLEND);
glEnable(GL_TEXTURE_2D);
我怎样画出三角形和直线?我认为每个人都应该有自己的VBO,对吗?
我通过在 glEnableVertexAttribArray
/glVertexAttribPointer
:
glBindBuffer
来解决这个问题。glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _indexBuffer);
glEnableVertexAttribArray(GLKVertexAttribPosition);
glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, Position));
glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, TexCoord));