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我正在尝试在 OpenGL 中制作模板蒙版。我一直在关注这个来源的模型（http://open.gl/depthstencils，更具体地说， http: //open.gl/content/code/c5_reflection.txt），据我所知，我有正确地遵循了这个例子。我的代码是绘制一个方形模板，然后在其上绘制另一个方形。我希望只看到第二个旋转绿色正方形中与第一个覆盖相同空间的部分。我实际看到的是两个重叠的正方形，一个旋转没有透明度。与示例的一个显着区别是我没有使用纹理。那是问题吗？我认为这将是一个更简单的例子。

我对 ES2.0 还很陌生，所以如果我在做一些明显愚蠢的事情，请告诉我。

初始化：

GLuint attributes[] = { GLKVertexAttribPosition, GLKVertexAttribColor, GLKVertexAttribTexCoord0 };
const char *attributeNames[] = { "position", "color", "texcoord0" };

// These are all global GLuint variables
// vshSrc and fshSrc are const char* filenames (the files are found properly)
_myProgram = loadProgram(vshSrc, fshSrc, 3, attributes, attributeNames);
_myProgramUniformMVP = glGetUniformLocation(_myProgram, "modelViewProjectionMatrix");
_myProgramUniformTex = glGetUniformLocation(_myProgram, "tex");
_myProgramUniformOverrideColor = glGetUniformLocation(_myProgram, "overrideColor");

绘制循环：

glEnable(GL_DEPTH_TEST);
glUseProgram(_myProgram);
glDisable(GL_BLEND);

  glClearColor(1.0, 1.0, 1.0, 1.0);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

  GLfloat gSquare[20] = { // not using the textures currently
    // posX, posY, posZ,     texX, texY,
    -0.5f, -0.5f, 0,        0.0f, 0.0f,
    0.5f, -0.5f, 0,         1.0f, 0.0f,
    -0.5f, 0.5f, 0,         0.0f, 1.0f,
    0.5f, 0.5f, 0,         1.0f, 1.0f
  };

  // Projection matrix
  float aspect = fabsf(self.view.bounds.size.width / self.view.bounds.size.height);
  GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(65.0f), aspect, 0.1f, 100.0f);
  // Put the squares where they can be seen
  GLKMatrix4 baseModelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, -4.0f);

  glEnable(GL_STENCIL_TEST);

  // Build the stencil
  glStencilFunc(GL_ALWAYS, 1, 0xFF); // Set any stencil to 1
  glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
  glStencilMask(0xFF); // Write to stencil buffer
  glDepthMask(GL_FALSE); // Don't write to depth buffer
  glClear(GL_STENCIL_BUFFER_BIT); // Clear stencil buffer (0 by default)

  GLKMatrix4 mvp = GLKMatrix4Multiply(projectionMatrix, baseModelViewMatrix);

  // Draw a stationary red square for the stencil (though the color shouldn't matter)
  glUniformMatrix4fv(_chetProgramUniformMVP, 1, 0, mvp.m);
  glUniform1i(_chetProgramUniformTex, 0);
  glUniform4f(_chetProgramUniformOverrideColor, 1.0f, 1.0f, 1.0f,0.0f);

  glVertexAttrib4f(GLKVertexAttribColor, 1, 0, 0, 1);
  glEnableVertexAttribArray(GLKVertexAttribPosition);
  glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, 20, gSquare);
  glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);



  // Prepare the mask
  glStencilFunc(GL_EQUAL, 1, 0xFF); // Pass test if stencil value is 1
  glStencilMask(0x00); // Don't write anything to stencil buffer
  glDepthMask(GL_TRUE); // Write to depth buffer

  glUniform4f(_myProgramUniformOverrideColor, 0.3f, 0.3f, 0.3f,1.0f);

  // A slow rotating green square to be masked by the stencil
  static float rotation = 0;
  rotation += 0.01;
  baseModelViewMatrix = GLKMatrix4Rotate(baseModelViewMatrix, rotation, 0, 0, 1);
  mvp = GLKMatrix4Multiply(projectionMatrix, baseModelViewMatrix);

  glUniformMatrix4fv(_myProgramUniformMVP, 1, 0, mvp.m);//The transformation matrix
  glUniform1i(_myProgramUniformTex, 0); // The texture
  glVertexAttrib4f(GLKVertexAttribColor, 0, 1, 0, 1);
  glEnableVertexAttribArray(GLKVertexAttribPosition);
  glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, 20, gSquare);
  glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

  glDisable(GL_STENCIL_TEST);

编辑：以下着色器内容与我遇到的问题无关。模板不会在着色器中进行。

顶点着色器：

attribute vec4 position;
attribute vec4 color;
attribute vec2 texcoord0;

varying lowp vec4 colorVarying;
varying lowp vec2 texcoord;

uniform mat4 modelViewProjectionMatrix;
uniform vec4 overrideColor;
void main()
{
  colorVarying = overrideColor * color;
  texcoord = texcoord0;
  gl_Position = modelViewProjectionMatrix * position;
}

片段着色器：

varying lowp vec4 colorVarying;
varying lowp vec2 texcoord;

uniform sampler2D tex;

void main()
{
  gl_FragColor = colorVarying * texture2D(tex, texcoord);
}
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1 回答 1

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有必要初始化模板缓冲区。这是修复它的代码。

glGenRenderbuffersOES(1, &depthStencilRenderbuffer);
glBindRenderbufferOES(GL_RENDERBUFFER_OES, depthStencilRenderbuffer);
glRenderbufferStorageOES(GL_RENDERBUFFER_OES, GL_DEPTH24_STENCIL8_OES, framebufferWidth, framebufferHeight);
glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_DEPTH_ATTACHMENT_OES, GL_RENDERBUFFER_OES, depthStencilRenderbuffer);
glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_STENCIL_ATTACHMENT_OES, GL_RENDERBUFFER_OES, depthStencilRenderbuffer);
于 2014-06-09T04:53:28.227 回答