我嘗試實現像繪畫工具一樣的東西,並與刷子的問題阿爾法通道卡住。我的畫筆是具有透明背景的.PNG紋理。我繪製在RGBA緩衝區中。我的代碼:在緩衝區中繪畫。問題與阿爾法香奈爾
initFBO(...)
...
glEnable(GL_BLEND);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
glBindFramebuffer(GL_FRAMEBUFFER, FBO);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
drawBrush(...)
glBindFramebuffer(GL_FRAMEBUFFER, 0);
drawFBO(...)
它的工作原理,但如果我停止我的刷,刷從alpha通道將在緩衝區從更換顏色積累。
我不熟悉,在OpenGL太近混合,並有問題與混合參數。我在混合或其他方面存在問題嗎?
更新:
initFBO(GLuint &framebuff, GLuint &text)
{
glGenFramebuffers(1, &framebuff);
glBindFramebuffer(GL_FRAMEBUFFER, framebuff);
glGenTextures(1, &text);
glBindTexture(GL_TEXTURE_2D, text);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, screenWidth, screenHeight, 0, GL_RGB, GL_FLOAT, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, text, 0);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
drawBrush(glm::vec2 mousePosition, GLuint texture, Shader shader)
{
glm::mat4 model;
model = glm::translate(model, glm::vec3(mousePosition, 1.0));
GLfloat brushVertices[] =
{
-0.1f, 0.1f, 0.0f, 0.0f, 1.0f,
-0.1f,-0.1f, 0.0f, 0.0f, 0.0f,
0.1f, 0.1f, 0.0f, 1.0f, 1.0f,
0.1f,-0.1f, 0.0f, 1.0f, 0.0f
};
glGenVertexArrays(1, &brushVAO);
glGenBuffers(1, &brushVBO);
glBindVertexArray(brushVAO);
glBindBuffer(GL_ARRAY_BUFFER, brushVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(brushVertices), &brushVertices, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)0);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
glBindVertexArray(0);
shader.set();
glUniform1i(glGetUniformLocation(shader.Program, "texture"), 0);
glUniformMatrix4fv(glGetUniformLocation(shader.Program, "model"), 1, GL_FALSE, glm::value_ptr(model));
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture);
glBindVertexArray(brushVAO);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glBindVertexArray(0);
}
drawFBO(GLuint texture, Shader shader)
{
GLfloat screenquadVertices[] =
{
-1.0f, 1.0f, 0.0f, 0.0f, 1.0f,
-1.0f, -1.0f,0.0f, 0.0f, 0.0f,
1.0f, 1.0f, 0.0f, 1.0f, 1.0f,
1.0f, -1.0f, 0.0f, 1.0f, 0.0f
};
glGenVertexArrays(1, &screenquadVAO);
glGenBuffers(1, &screenquadVBO);
glBindVertexArray(screenquadVAO);
glBindBuffer(GL_ARRAY_BUFFER, screenquadVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(screenquadVertices), &screenquadVertices, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)0);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
glBindVertexArray(0);
shader.set();
glUniform1i(glGetUniformLocation(shader.Program, "texture"), 0);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture);
glBindVertexArray(screenquadVAO);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glBindVertexArray(0);
}
UPDATE2
確定。我嘗試了你的推薦,但結果是相似的,並沒有解釋我的問題。看看:
1)glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
和兩個預乘.PNG紋理 - 黑色和白色。
2)glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
和直-α質地。
是否禁用了深度測試? – dari
是的。如果我使它沒有改變。 – OpenGLNoob
您發佈的圖片 - 這是什麼圖片?什麼是「畫FBO」代碼,「畫筆」代碼,以及您是如何設置FBO的? – ybungalobill