transform feedback object 理解

最新推荐文章于 2024-11-07 23:44:50 发布

wodownload2

最新推荐文章于 2024-11-07 23:44:50 发布

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分类专栏： opengl 文章标签： transform feedback object

本文链接：https://blog.youkuaiyun.com/wodownload2/article/details/97805256

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本文深入探讨了使用OpenGL和transform feedback技术进行粒子系统实时更新的方法。通过详细的代码解析，展示了如何利用GPU加速粒子效果的更新过程，包括新粒子的生成与旧粒子的状态更新，实现了高效的粒子渲染。

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void UpdateParticle()
{
	//printf("current particle buffer tfo %d %d\n",currentParticleTFO, currentParticleTFOForDraw);
	int currentOldParticleBufferIndex = currentParticleTFOForDraw;
	if (particleCount==-1)
	{
		particleCount++;
	}
	else
	{
		glGetQueryObjectiv(queryObject, GL_QUERY_RESULT,&particleCount);
	}
	GL_CALL(glEnable(GL_RASTERIZER_DISCARD));
	glBindTransformFeedback(GL_TRANSFORM_FEEDBACK, updateParticleTFO[currentParticleTFO]);
	glBeginQuery(GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN, queryObject);
	glUseProgram(updateParticleProgram);
	glBeginTransformFeedback(GL_POINTS);
	//new emitted particle update
	if (bEmitNewParticle)
	{
		bEmitNewParticle = false;
		//update particle : write new particle to some buffer via transform feedback technique
		glBindBuffer(GL_ARRAY_BUFFER, tfoNewParticleBuffer);
		glEnableVertexAttribArray(updateParticleProgramPosLocation);
		glVertexAttribPointer(updateParticleProgramPosLocation, 4, GL_FLOAT, GL_FALSE, sizeof(float) * 4, 0);
		glBindBuffer(GL_ARRAY_BUFFER, 0);
		glDrawTransformFeedback(GL_POINTS, tfoNewParticle);
	}
	//update old particle : write old particle to some buffer via transform feedback technique
	if (particleCount>0)
	{
		glBindBuffer(GL_ARRAY_BUFFER, updateParticleTFOBuffer[currentOldParticleBufferIndex]);
		glEnableVertexAttribArray(updateParticleProgramPosLocation);
		glVertexAttribPointer(updateParticleProgramPosLocation, 4, GL_FLOAT, GL_FALSE, sizeof(float) * 4, 0);
		glBindBuffer(GL_ARRAY_BUFFER, 0);
		glDrawTransformFeedback(GL_POINTS, updateParticleTFO[currentOldParticleBufferIndex]);
	}
	glEndTransformFeedback();
	glEndQuery(GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN);
	glUseProgram(0);
	glDisable(GL_RASTERIZER_DISCARD);
	glBindTransformFeedback(GL_TRANSFORM_FEEDBACK, 0);
	currentParticleTFOForDraw = currentParticleTFO;

	//glBindBuffer(GL_ARRAY_BUFFER, updateParticleTFOBuffer[currentParticleTFOForDraw]);
	//FloatBundle*vertexes = (FloatBundle*)glMapBuffer(GL_ARRAY_BUFFER, GL_READ_ONLY);
	//printf("%f,%f,%f,%f\n",vertexes[0].v[0], vertexes[0].v[1], vertexes[0].v[3], vertexes[0].v[3]);
	//glUnmapBuffer(GL_ARRAY_BUFFER);
	//glBindBuffer(GL_ARRAY_BUFFER, 0);
	currentParticleTFO = (currentParticleTFO + 1) % 2;
}