カラーピッキングを使用して 3D オブジェクトを選択することについてです。メッシュ (更新: 静的ヘッダー ファイルに存在し、同じプロジェクトの画面に正常に表示されます) を新しいオフスクリーン フレームバッファーに描画し、glReadPixels を使用してユーザーがタッチしたかどうかを識別します。
Erik M.Buck による本「Learning OpenGLES for iOS」のプロジェクト opengles_ch10_1 のコードに従って、選択した (タップして) ピクセルの色 0,0,0 を常に nslog に出力する次のコードを作成しました。
私のコードは次のとおりです。
- (IBAction) tapGesture:(id)sender
{
if ([(UITapGestureRecognizer *)sender state] == UIGestureRecognizerStateEnded) {
CGPoint tapLocation = [(UITapGestureRecognizer *)sender locationInView:self.view];
int tt = [self findMeshByPoint:tapLocation];
//NSLog( @"tap value: %i", tt );
}
}
- (NSUInteger)findMeshByPoint:(CGPoint)point
{
//In openGL the y axis starts from the bottom of the screen
point.y = self.view.bounds.size.height - point.y;
GLKView *glView = (GLKView *)self.view;
NSAssert([glView isKindOfClass:[GLKView class]],
@"View controller's view is not a GLKView");
// Make the view's context current
[EAGLContext setCurrentContext:glView.context];
glBindVertexArrayOES(0);
// self.effect.constantColor = GLKVector4Make( 1.0f, //This should be meshId/255.0f
if(0 == _glVertexAttributeBufferID)
{
GLuint glName;
glGenBuffers(1, // STEP 1
&glName);
glBindBuffer(GL_ARRAY_BUFFER, // STEP 2
glName);
glBufferData( // STEP 3
GL_ARRAY_BUFFER, // Initialize buffer contents
sizeof(parparit51OBJVertices), parparit51OBJVertices,
GL_STATIC_DRAW); // Hint: cache in GPU memory
_glVertexAttributeBufferID = glName;
}
else
{
glBindBuffer(GL_ARRAY_BUFFER,
_glVertexAttributeBufferID);
}
//glEnableVertexAttribArray(TETerrainPositionAttrib);
glEnableVertexAttribArray( GLKVertexAttribPosition );
if(0 == _program)
{
[self loadShadersWithName:@"UtilityPickTerrainShader"];
[self buildFBO];
NSAssert(0 != _program,
@"prepareOpenGL failed to load shaders");
}
glUseProgram(_program);
// Pre-calculate the mvpMatrix
GLKMatrix4 modelViewProjectionMatrix2 =
GLKMatrix4Multiply(
self.effect.transform.projectionMatrix,
self.effect.transform.modelviewMatrix);
// Standard matrices
glUniformMatrix4fv(uniforms[UtilityPickTerrainMVPMatrix], 1, 0,
modelViewProjectionMatrix2.m);
// glUniform2fv(uniforms[UtilityPickTerrainDimensionFactors], 1,
// &_temp1 ); //self.factors.v); //I removed this from the shaders
glUniform1f(uniforms[UtilityPickTerrainModelIndex],
1.0f ); // self.modelIndex / 255.0f);
glBindFramebuffer(GL_FRAMEBUFFER, _pickFBO);
glViewport(0, 0, 512, 512);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//glEnableVertexAttribArray(GLKVertexAttribPosition);
glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, 12 * sizeof(GLfloat), 0);
NSLog( @"******* 7" );
[self.effect prepareToDraw];
glDrawArrays(GL_TRIANGLES, 0, sizeof(parparit51OBJVertices) / sizeof(Vertex));
NSLog( @"******* 7.5" );
const GLfloat width = [glView drawableWidth];
const GLfloat height = [glView drawableHeight];
NSAssert(0 < width && 0 < height, @"Invalid drawble size");
// Get info for picked location
const GLKVector2 scaledProjectionPosition = {
point.x / width,
point.y / height
};
NSLog( @"******* 8" );
GLubyte pixelColor[4]; // Red, Green, Blue, Alpha color
GLint readLocationX = MIN((512 - 1),
(512 - 1) * scaledProjectionPosition.x);
GLint readLocationY = MIN((512 - 1),
(512 - 1) * scaledProjectionPosition.y);
glReadPixels(readLocationX,
readLocationY,
1,
1,
GL_RGBA,
GL_UNSIGNED_BYTE,
pixelColor);
NSLog(@"pixelColor[0]=%i, pixelColor[1]=%i, pixelColor[2]=%i", pixelColor[0], pixelColor[1], pixelColor[2] );
// Restore OpenGL state that pickTerrainEffect changed
glBindFramebuffer(GL_FRAMEBUFFER, 0); // default frame buffer
glViewport(0, 0, width, height); // full area of glView
return 0;
}
-(void) buildFBO
{
if ( 0 == _pickFBO )
{
GLuint colorTexture;
// Create a texture object to apply to model
glGenTextures(1, &colorTexture);
glBindTexture(GL_TEXTURE_2D, colorTexture);
// Set up filter and wrap modes for this texture object
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,
GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,
GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,
GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
GL_LINEAR_MIPMAP_LINEAR);
// Allocate a texture image we can render into
// Pass NULL for the data parameter since we don't need to
// load image data. We will be generating the image by
// rendering to this texture.
glTexImage2D(GL_TEXTURE_2D,
0,
GL_RGBA,
512,
512,
0,
GL_RGBA,
GL_UNSIGNED_BYTE,
NULL);
GLuint depthRenderbuffer;
glGenRenderbuffers(1, &depthRenderbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, depthRenderbuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16,
512, 512);
glGenFramebuffers(1, &_pickFBO);
glBindFramebuffer(GL_FRAMEBUFFER, _pickFBO);
glFramebufferTexture2D(GL_FRAMEBUFFER,
GL_COLOR_ATTACHMENT0,
GL_TEXTURE_2D, colorTexture, 0);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthRenderbuffer);
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) !=
GL_FRAMEBUFFER_COMPLETE)
{
NSLog(@"failed to make complete framebuffer object %x", glCheckFramebufferStatus(GL_FRAMEBUFFER));
//+++tbd+++UtilityPickTerrainEffectDestroyFBO(fboName);
return;
}
//#ifdef DEBUG
// { // Report any errors
GLenum error = glGetError();
if(GL_NO_ERROR != error)
{
NSLog(@"GL Error: 0x%x", error);
}
// }
//#endif
}
}