Jump to content
  • Advertisement
Sign in to follow this  

OpenGL My opengl program is really slow, what's the problem?

This topic is 1852 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hi, i'm a beginner with opengl, now i'm trying to load in my program few 3d models and to use some shaders but the problem is that is all already too slow.

I'm loading 2 models, one of them has 39282 vertices and 69451 faces, i know it's much but i thought having only 2 models would not have been problem.

It takes a lot for loading the models and then I have an average of 13 fps (i know fps are not so accurate but for now I think for me are enough) in the scene.

This is my scene:



When I load the models, i use assimp for copying the vertices, normals, uvs and faces in some std::vectors (the ones of my model class), i create the vbos and vao for them and i store the model information in another vector inside my scene object, then when i draw the scene, i scan all the models i have and and use this code for drawing:

(note: this is the code in my renderer class so in the upper section i have the vbo and vao set up i talked about earlier and in the lower the drawing section.)

#include "renderer.h"
#include <math.h>

Renderer::Renderer(Mesh* mesh, Material* material) :
	glGenVertexArrays(1, &vao);

	glGenBuffers(1, &indexBuffer);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, mesh->faces().size() * sizeof(unsigned int), &mesh->faces()[0], GL_STATIC_DRAW);

	glGenBuffers(1, &vertexBuffer);
	glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
	glBufferData(GL_ARRAY_BUFFER, mesh->numVertices() * sizeof(glm::vec3), &mesh->vertices()[0], GL_STATIC_DRAW);

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
	glGenBuffers(1, &uvBuffer);
	glBindBuffer(GL_ARRAY_BUFFER, uvBuffer);
	glBufferData(GL_ARRAY_BUFFER, mesh->uvs().size() * sizeof(glm::vec2), &mesh->uvs()[0], GL_STATIC_DRAW);
	glVertexAttribPointer(1, 2, GL_FLOAT, GL_TRUE, 0, 0);

	glGenBuffers(1, &normalBuffer);
	glBindBuffer(GL_ARRAY_BUFFER, normalBuffer);
	glBufferData(GL_ARRAY_BUFFER, mesh->normals().size() * sizeof(glm::vec3), &mesh->normals()[0], GL_STATIC_DRAW);

	glVertexAttribPointer(2, 3, GL_FLOAT, GL_TRUE, 0, 0);


void Renderer::draw(Camera* camera,  glm::mat4 model, Light* light) {
	_material->shader()->setUniform("camera", camera->matrix());
	_material->shader()->setUniform("model", model);
	//_material->shader()->setUniform("view", camera->view());
//	_material->shader()->setUniform("tex", 0); //to use GL_TEXTURE0
	_material->shader()->setUniform("roughness", _material->roughness());
	float Ks = ((_material->roughness()+8)/(8*3.141592));
	_material->shader()->setUniform("Kd", _material->color() / 3.141592f);
	_material->shader()->setUniform("Ks", _material->specularColor() * Ks);

	_material->shader()->setUniform("lightPos", light->_position);
	_material->shader()->setUniform("intensity", light->_intensity * light->_color);
	//_material->shader()->setUniform("light.attenuation", light->_attenuation);
	//_material->shader()->setUniform("light.ambientCoefficient", light->_ambientCoefficient);
	_material->shader()->setUniform("cameraPos", camera->position());
	glBindTexture(GL_TEXTURE_2D, _material->texture()->getID());
	//Bind vao and draw
	//glDrawArrays(GL_TRIANGLES, 0, _mesh->numVertices());
	glDrawElements(GL_TRIANGLES, _mesh->faces().size(), GL_UNSIGNED_INT, 0);

	glBindTexture(GL_TEXTURE_2D, 0);


(some of the code is commented because i'm doing some tests)


It's my rendering code bad? Can you say me what's the problem, why is everything so slow?

Thanks in advance for the help



Share this post

Link to post
Share on other sites

Just going on whats been posted its difficult to tell (what hardware is it running on?), but two areas I would look at, 1 try using unsigned short for the index type if possible. 2, your shaders are being set by string, not sure how thats done, is it doing a lookup every frame? are you using the string to get the uniform index every frame? if so, try getting the uniform location once, when the shader loads and links.

Share this post

Link to post
Share on other sites

I think the hardware it's fast enough, i have an amd hd 7950 gpu and a intel i5 3570k cpu both overclocked.

1) thanks for the advice, i will use unsigned short for the indices, in this test my model has more faces than the maximum unsigned short supported but i think i will have lighter models so it should work.

2) the drawing method is called one time per frame per model in the scene,

the shader-> use() is as follows:

void Program::use() const {



where ID is a GLuint representing the shader compiled and linked.


This is how the setUniform() works:

GLint Program::uniform(const GLchar* uniformName) const {
		throw std::runtime_error("uniformName is NULL");

	GLint uniform = glGetUniformLocation(_ID, uniformName);
	if(uniform == -1)
		throw std::runtime_error(std::string("Program uniform not found: ") + uniformName);

	return uniform;

void Program::setUniform(const GLchar* uniformName, GLint v0) {
	glUniform1i(uniform(uniformName), v0);

void Program::setUniform(const GLchar* uniformName, const glm::mat4& m) {
	glUniformMatrix4fv(uniform(uniformName), 1, GL_FALSE, glm::value_ptr(m));

void Program::setUniform(const GLchar* uniformName, const glm::vec3& v) {
	glUniform3fv(uniform(uniformName), 1, glm::value_ptr(v));

void Program::setUniform(const GLchar* uniformName, GLfloat v0) {
	glUniform1f(uniform(uniformName), v0);


and these are the other parts used in the method:


bool Program::isInUse() const {
	GLint currentProgram = 0;
	glGetIntegerv(GL_CURRENT_PROGRAM, &currentProgram);
	return (currentProgram == (GLint)_ID);

void Program::stopUsing() const {


So yes, for every model, every frame i set and unset the program to be used and set the uniform variables. If this is the problem, where it's better to set the uniforms?

Share this post

Link to post
Share on other sites

There have been times ive found glGetUniformLocation being called too often during run time to be a problem, after building the shader get the uniform location and save it, look it up locally at run time and by pass calling glGetUniformLocation at run time, unless the shader changes dynamically the location shouldnt change.


Also, you may not always want to consider -1 locations as incorrect, -1 uniform locations can mean a few things. If the shader doesnt make use of a uniform, either it was optimized out or commented out but still declared, the shader may run fine even with a uniform having a -1 location, it doesnt always mean a the uniform had a typo or wasnt found.


my model has more faces than the maximum unsigned short supported


the index buffer indexes vertices, not faces, many faces may share the same vertex, reducing the vertex count, the whole purpose of index buffers. So if the numbers from your first post are correct the vertex count easily fits in unsigned short.



In general dont call the "glGet*()" series of commands as they stall rendering to retrieve the state being asked for.

So assert(isInUse()); calls glGetInteger() which is probably the problem, comment all those out.

Edited by NumberXaero

Share this post

Link to post
Share on other sites

Hi, sorry for the late reply.

So i tried to change the code so the get uniform location is called only once(i was confused about the getuniformlocation, i did not realize that it actully gives me the uniform position, so thanks now it's more clear), in the constructor of my program class like this:

Program::Program() : 
	_ID = LoadShaders("shaders/Blinn-Phong.vs", "shaders/Blinn-Phong.fs");
	_cam = uniform("camera");
	_mod = uniform("model");
	_rough = uniform("roughness");
	_kd = uniform("Kd");
	_ks = uniform("Ks");
	_lightPos = uniform("lightPos");
	_int = uniform("intensity");
	_camPos = uniform("cameraPos");

GLint Program::uniform(const GLchar* uniformName) const {
		throw std::runtime_error("uniformName is NULL");

	GLint uniform = glGetUniformLocation(_ID, uniformName);
	if(uniform == -1)
		throw std::runtime_error(std::string("Program uniform not found: ") + uniformName);

	return uniform;


(the uniform == -1 is still there but i'll change it)


and then set the uniforms without getting again the location: 

GLint Program::uniform(ShProp type) const {
	switch(type) {
	case CAMERA:
		return _cam;
	case MODEL:
		return _mod;
		return _rough;
	case KD:
		return _kd;
	case KS:
		return _ks;
		return _lightPos;
		return _int;
		return _camPos;
	default: return -1;

void Program::setUniform(ShProp type, GLint v0) {
	glUniform1i(uniform(type), v0);

void Program::setUniform(ShProp type, const glm::mat4& m) {
	glUniformMatrix4fv(uniform(type), 1, GL_FALSE, glm::value_ptr(m));

void Program::setUniform(ShProp type, const glm::vec3& v) {
	glUniform3fv(uniform(type), 1, glm::value_ptr(v));

void Program::setUniform(ShProp type, GLfloat v0) {
	glUniform1f(uniform(type), v0);


(for now the code is like this because i'm testing)


I also removed the asserts with the glGetIntegerv call but i'm continuing to have 13 fps, and this despite where i'm looking, they never go down or up.

So I have the same problem.


As for the index buffer part, I tried using unsigned shorts but after that my rabbit mesh was all messed up so i changed it back to unsigned int.

Edited by uselessChiP

Share this post

Link to post
Share on other sites

If its not caused by the state queries from glGet*() calls, then it probably related to the drawing calls, unless its something somewhere else.


When you changed to unsigned short, did you also make sure to change all the GL_UNSIGNED_INT's to GL_UNSIGNED_SHORT and all the sizeof(unsigned int) across all the buffer setup calls and draw calls?


You said the fps are not accurate in your first post, is the scene sluggish? can you profile where the time is being consumed? if not, make sure the fps are correct so you have a solid value to go by.


You might try bypassing vaos and just binding buffers and enabling arrays at draw time. I had a problem once with vertex array objects causing problems, it was related to the way the gl functions were being loaded by glew, it required glewExperimental set to true before calling glewInit(), not sure if its was on amd or nvidia. Im not sure how youre loading gl calls, maybe its relevant. Valve software released a doc "Porting source to linux" where they said vaos were slower then glVertexAttribPointer on all implementations.


Depending on your targeted GL version you might want to look at the gl_vertex_attrib_binding extension.

Share this post

Link to post
Share on other sites

Comment out the draw code except for swapBuffers() or whatever you call when done drawing. Sounds like you have a Sleep() call in your application. Or you are doing something very stupid each frame like re-loading your models.


glGet commands are not even close to that slow and you only have a few models. You should be fine. Is the framerate actually choppy or are you calculating it yourself (it could be wrong try FRAPS).

Share this post

Link to post
Share on other sites


if for drawing calls you mean the glDrawElements, i call them like this:


this is the main loop:

double lastTime = glfwGetTime();
	do {

		glClearColor(0.0f, 0.4f, 0.0f,1.0f);

		double thisTime = glfwGetTime();
		float secondElapsed = thisTime - lastTime;
		lastTime = thisTime;




	} while(!glfwGetKey(GLFW_KEY_ESC) && glfwGetWindowParam(GLFW_OPENED) && !glfwGetKey('P'));


this is the method draw(that draw every object in the scene, 2 in this case)

void draw() {


and this is the scene->draw() implementation:

void Scene::draw() {
	for(unsigned int i = 0; i < _model.size(); i++) {
		_model->renderer()->draw(_camera[_activeCamera], _model->transform(),  _light[0]);


the renderer()->draw... is the one i posted above:

void Renderer::draw(Camera* camera,  glm::mat4 model, Light* light) {

	_material->shader()->setUniform(CAMERA, camera->matrix());
	_material->shader()->setUniform(MODEL, model);
//	_material->shader()->setUniform("tex", 0); //to use GL_TEXTURE0

	_material->shader()->setUniform(ROUGHNESS, _material->roughness());
	float Ks = ((_material->roughness()+8)/(8*3.141592));
	_material->shader()->setUniform(KD, _material->color() / 3.141592f);
	_material->shader()->setUniform(KS, _material->specularColor() * Ks);
	_material->shader()->setUniform(LIGHTPOS, light->_position);
	_material->shader()->setUniform(INTENSITY, light->_intensity * light->_color);
	//_material->shader()->setUniform("light.attenuation", light->_attenuation);
	//_material->shader()->setUniform("light.ambientCoefficient", light->_ambientCoefficient);
	_material->shader()->setUniform(CAMERAPOS, camera->position());
	glBindTexture(GL_TEXTURE_2D, _material->texture()->getID());
	//Bind vao and draw
	//glDrawArrays(GL_TRIANGLES, 0, _mesh->numVertices());
	glDrawElements(GL_TRIANGLES, _mesh->faces().size(), GL_UNSIGNED_INT, 0);

	//glBindTexture(GL_TEXTURE_2D, 0);




As for fps, im using fraps to measure them so i think they are accurate and also i feel that all is slow moving around the scene.

For the last part(the one bypassing vaos) im not sure to understand what you mean also my target platform for now is windows and i'm also using glewExperimental.





I don't think i have a sleep call, commenting the draw code makes the program go fast but this also happens when im not loading the rabbit, as for the loading the model every frame i think im loading them once: im loading the vertices, normals uv coordinates once in some vectors, then i bind once the data to some vertex buffers in my drawing code im only setting the uniforms binding the vao and drawing.

Share this post

Link to post
Share on other sites

You are passing the glm::mat4 parameter to your draw method by value. I should think that was a bad idea. You should pass it by reference, otherwise the mat4 object gets copied to the stack on every call. Whether that's a major contributor to your performance issues or not, only profiling would say for sure, but it's a good idea in any case.

Share this post

Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
  • Advertisement
  • Popular Tags

  • Similar Content

    • By nOoNEE
      i am reading this book : link
      in the OpenGL Rendering Pipeline section there is a picture like this: link
      but the question is this i dont really understand why it is necessary to turn pixel data in to fragment and then fragment into pixel could please give me a source or a clear Explanation that why it is necessary ? thank you so mu
    • By Inbar_xz
      I'm using the OPENGL with eclipse+JOGL.
      My goal is to create movement of the camera and the player.
      I create main class, which create some box in 3D and hold 
      an object of PlayerAxis.
      I create PlayerAxis class which hold the axis of the player.
      If we want to move the camera, then in the main class I call to 
      the func "cameraMove"(from PlayerAxis) and it update the player axis.
      That's work good.
      The problem start if I move the camera on 2 axis, 
      for example if I move with the camera right(that's on the y axis)
      and then down(on the x axis) -
      in some point the move front is not to the front anymore..
      In order to move to the front, I do
      player.playerMoving(0, 0, 1);
      And I learn that in order to keep the front move, 
      I need to convert (0, 0, 1) to the player axis, and then add this.
      I think I dont do the convert right.. 
      I will be glad for help!

      Here is part of my PlayerAxis class:
      //player coordinate float x[] = new float[3]; float y[] = new float[3]; float z[] = new float[3]; public PlayerAxis(float move_step, float angle_move) { x[0] = 1; y[1] = 1; z[2] = -1; step = move_step; angle = angle_move; setTransMatrix(); } public void cameraMoving(float angle_step, String axis) { float[] new_x = x; float[] new_y = y; float[] new_z = z; float alfa = angle_step * angle; switch(axis) { case "x": new_z = addVectors(multScalar(z, COS(alfa)), multScalar(y, SIN(alfa))); new_y = subVectors(multScalar(y, COS(alfa)), multScalar(z, SIN(alfa))); break; case "y": new_x = addVectors(multScalar(x, COS(alfa)), multScalar(z, SIN(alfa))); new_z = subVectors(multScalar(z, COS(alfa)), multScalar(x, SIN(alfa))); break; case "z": new_x = addVectors(multScalar(x, COS(alfa)), multScalar(y, SIN(alfa))); new_y = subVectors(multScalar(y, COS(alfa)), multScalar(x, SIN(alfa))); } x = new_x; y = new_y; z = new_z; normalization(); } public void playerMoving(float x_move, float y_move, float z_move) { float[] move = new float[3]; move[0] = x_move; move[1] = y_move; move[2] = z_move; setTransMatrix(); float[] trans_move = transVector(move); position[0] = position[0] + step*trans_move[0]; position[1] = position[1] + step*trans_move[1]; position[2] = position[2] + step*trans_move[2]; } public void setTransMatrix() { for (int i = 0; i < 3; i++) { coordiTrans[0][i] = x[i]; coordiTrans[1][i] = y[i]; coordiTrans[2][i] = z[i]; } } public float[] transVector(float[] v) { return multiplyMatrixInVector(coordiTrans, v); }  
      and in the main class i have this:
      public void keyPressed(KeyEvent e) { if (e.getKeyCode()== KeyEvent.VK_ESCAPE) { System.exit(0); //player move } else if (e.getKeyCode()== KeyEvent.VK_W) { //front //moveAmount[2] += -0.1f; player.playerMoving(0, 0, 1); } else if (e.getKeyCode()== KeyEvent.VK_S) { //back //moveAmount[2] += 0.1f; player.playerMoving(0, 0, -1); } else if (e.getKeyCode()== KeyEvent.VK_A) { //left //moveAmount[0] += -0.1f; player.playerMoving(-1, 0, 0); } else if (e.getKeyCode()== KeyEvent.VK_D) { //right //moveAmount[0] += 0.1f; player.playerMoving(1, 0, 0); } else if (e.getKeyCode()== KeyEvent.VK_E) { //moveAmount[0] += 0.1f; player.playerMoving(0, 1, 0); } else if (e.getKeyCode()== KeyEvent.VK_Q) { //moveAmount[0] += 0.1f; player.playerMoving(0, -1, 0); //camera move } else if (e.getKeyCode()== KeyEvent.VK_I) { //up player.cameraMoving(1, "x"); } else if (e.getKeyCode()== KeyEvent.VK_K) { //down player.cameraMoving(-1, "x"); } else if (e.getKeyCode()== KeyEvent.VK_L) { //right player.cameraMoving(-1, "y"); } else if (e.getKeyCode()== KeyEvent.VK_J) { //left player.cameraMoving(1, "y"); } else if (e.getKeyCode()== KeyEvent.VK_O) { //right round player.cameraMoving(-1, "z"); } else if (e.getKeyCode()== KeyEvent.VK_U) { //left round player.cameraMoving(1, "z"); } }  
      finallt found it.... i confused with the transformation matrix row and col. thanks anyway!
    • By Lewa
      So, i'm currently trying to implement an SSAO shader from THIS tutorial and i'm running into a few issues here.
      Now, this SSAO method requires view space positions and normals. I'm storing the normals in my deferred renderer in world-space so i had to do a conversion and reconstruct the position from the depth buffer.
      And something there goes horribly wrong (which has probably to do with worldspace to viewspace transformations).
      (here is the full shader source code if someone wants to take a look at it)
      Now, i suspect that the normals are the culprit.
      vec3 normal = ((uNormalViewMatrix*vec4(normalize(texture2D(sNormals, vTexcoord).rgb),1.0)).xyz); "sNormals" is a 2D texture which stores the normals in world space in a RGB FP16 buffer.
      Now i can't use the camera viewspace matrix to transform the normals into viewspace as the cameras position isn't set at (0,0,0), thus skewing the result.
      So what i did is to create a new viewmatrix specifically for this normal without the position at vec3(0,0,0);
      //"camera" is the camera which was used for rendering the normal buffer renderer.setUniform4m(ressources->shaderSSAO->getUniform("uNormalViewMatrix"), glmExt::createViewMatrix(glm::vec3(0,0,0),camera.getForward(),camera.getUp())//parameters are (position,forwardVector,upVector) ); Though i have the feeling this is the wrong approach. Is this right or is there a better/correct way of transforming a world space normal into viewspace?
    • By HawkDeath
      I'm trying mix two textures using own shader system, but I have a problem (I think) with uniforms.
      Code: https://github.com/HawkDeath/shader/tree/test
      To debug I use RenderDocs, but I did not receive good results. In the first attachment is my result, in the second attachment is what should be.
      PS. I base on this tutorial https://learnopengl.com/Getting-started/Textures.

    • By norman784
      I'm having issues loading textures, as I'm clueless on how to handle / load images maybe I missing something, but the past few days I just google a lot to try to find a solution. Well theres two issues I think, one I'm using Kotlin Native (EAP) and OpenGL wrapper / STB image, so I'm not quite sure wheres the issue, if someone with more experience could give me some hints on how to solve this issue?
      The code is here, if I'm not mistaken the workflow is pretty straight forward, stbi_load returns the pixels of the image (as char array or byte array) and you need to pass those pixels directly to glTexImage2D, so a I'm missing something here it seems.
    • By Hashbrown
      I've noticed in most post processing tutorials several shaders are used one after another: one for bloom, another for contrast, and so on. For example: 
      postprocessing.quad.bind() // Effect 1 effect1.shader.bind(); postprocessing.texture.bind(); postprocessing.quad.draw(); postprocessing.texture.unbind(); effect1.shader.unbind(); // Effect 2 effect2.shader.bind(); // ...and so on postprocessing.quad.unbind() Is this good practice, how many shaders can I bind and unbind before I hit performance issues? I'm afraid I don't know what the good practices are in open/webGL regarding binding and unbinding resources. 
      I'm guessing binding many shaders at post processing is okay since the scene has already been updated and I'm just working on a quad and texture at that moment. Or is it more optimal to put shader code in chunks and bind less frequently? I'd love to use several shaders at post though. 
      Another example of what I'm doing at the moment:
      1) Loop through GameObjects, bind its phong shader (send color, shadow, spec, normal samplers), unbind all.
      2) At post: bind post processor quad, and loop/bind through different shader effects, and so on ...
      Thanks all! 
    • By phil67rpg
      void collision(int v) { collision_bug_one(0.0f, 10.0f); glutPostRedisplay(); glutTimerFunc(1000, collision, 0); } void coll_sprite() { if (board[0][0] == 1) { collision(0); flag[0][0] = 1; } } void erase_sprite() { if (flag[0][0] == 1) { glColor3f(0.0f, 0.0f, 0.0f); glBegin(GL_POLYGON); glVertex3f(0.0f, 10.0f, 0.0f); glVertex3f(0.0f, 9.0f, 0.0f); glVertex3f(1.0f, 9.0f, 0.0f); glVertex3f(1.0f, 10.0f, 0.0f); glEnd(); } } I am using glutTimerFunc to wait a small amount of time to display a collision sprite before I black out the sprite. unfortunately my code only blacks out the said sprite without drawing the collision sprite, I have done a great deal of research on the glutTimerFunc and  animation.
    • By Lewa
      So, i stumbled upon the topic of gamma correction.
      So from what i've been able to gather: (Please correct me if i'm wrong)
      Old CRT monitors couldn't display color linearly, that's why gamma correction was nessecary. Modern LCD/LED monitors don't have this issue anymore but apply gamma correction anyway. (For compatibility reasons? Can this be disabled?) All games have to apply gamma correction? (unsure about that) All textures stored in file formats (.png for example) are essentially stored in SRGB color space (as what we see on the monitor is skewed due to gamma correction. So the pixel information is the same, the percieved colors are just wrong.) This makes textures loaded into the GL_RGB format non linear, thus all lighting calculations are wrong You have to always use the GL_SRGB format to gamma correct/linearise textures which are in SRGB format  
      Now, i'm kinda confused how to proceed with applying gamma correction in OpenGL.
      First of, how can i check if my Monitor is applying gamma correction? I noticed in my monitor settings that my color format is set to "RGB" (can't modify it though.) I'm connected to my PC via a HDMI cable. I'm also using the full RGB range (0-255, not the 16 to ~240 range)
      What i tried to do is to apply a gamma correction shader shown in the tutorial above which looks essentially like this: (it's a postprocess shader which is applied at the end of the renderpipeline)
      vec3 gammaCorrection(vec3 color){ // gamma correction color = pow(color, vec3(1.0/2.2)); return color; } void main() { vec3 color; vec3 tex = texture2D(texture_diffuse, vTexcoord).rgb; color = gammaCorrection(tex); outputF = vec4(color,1.0f); } The results look like this:
      No gamma correction:
      With gamma correction:
      The colors in the gamma corrected image look really wased out. (To the point that it's damn ugly. As if someone overlayed a white half transparent texture. I want the colors to pop.)
      Do i have to change the textures from GL_RGB to GL_SRGB in order to gamma correct them in addition to applying the post process gamma correction shader? Do i have to do the same thing with all FBOs? Or is this washed out look the intended behaviour?
    • By OneKaidou
      I am trying to program shadow volumes and i stumbled upon an artifact which i can not find the cause for.
      I generate the shadow volumes using a geometry shader with reversed extrusion (projecting the lightfacing triangles to infinity) and write the stencil buffer according to z-fail. The base of my code is the "lighting" chapter from learnopengl.com, where i extended the shader class to include geometry shader. I also modified the "lightingshader" to draw the ambient pass when "pass" is set to true and the diffuse/ specular pass when set to false. For easier testing i added a view controls to switch on/off the shadow volumes' color rendering or to change the cubes' position, i made the lightnumber controllable and changed the diffuse pass to render green for easier visualization of my problem.
      The first picture shows the rendered scene for one point light, all cubes and the front cube's shadow volume is the only one created (intentional). Here, all is rendered as it should be with all lit areas green and all areas inside the shadow volume black (with the volume's sides blended over).

      If i now turn on the shadow volumes for all the other cubes, we get a bit of a mess, but its also obvious that some areas that were in shadow before are now erroneously lit (for example the first cube to the right from the originaly shadow volumed cube). From my testing the areas erroneously lit are the ones where more than one shadow volume marks the area as shadowed.

      To check if a wrong stencil buffer value caused this problem i decided to change the stencil function for the diffuse pass to only render if the stencil is equal to 2. As i repeated this approach with different values for the stencil function i found out that if i set the value equal to 1 or any other uneven value the lit and shadowed areas are inverted and if i set it to 0 or any other even value i get the results shown above.
      This lead me to believe that the value and thus the stencil buffer values may be clamped to [0,1] which would also explain the artifact, because twice in shadow would equal in no shadow at all, but from what i found on the internet and from what i tested with
      GLint stencilSize = 0; glGetFramebufferAttachmentParameteriv(GL_DRAW_FRAMEBUFFER, GL_STENCIL, GL_FRAMEBUFFER_ATTACHMENT_STENCIL_SIZE, &stencilSize); my stencilsize is 8 bit, which should be values within [0,255].
      Does anyone know what might be the cause for this artifact or the confusing results with other stencil functions?
      // [the following code includes all used gl* functions, other parts are due to readability partialy excluded] // glfw: initialize and configure // ------------------------------ glfwInit(); glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4); glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 4); glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); // glfw window creation // -------------------- GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL); if (window == NULL) { cout << "Failed to create GLFW window" << endl; glfwTerminate(); return -1; } glfwMakeContextCurrent(window); glfwSetFramebufferSizeCallback(window, framebuffer_size_callback); glfwSetCursorPosCallback(window, mouse_callback); glfwSetScrollCallback(window, scroll_callback); // tell GLFW to capture our mouse glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED); // glad: load all OpenGL function pointers // --------------------------------------- if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) { cout << "Failed to initialize GLAD" << endl; return -1; } // ==================================================================================================== // window and functions are set up // ==================================================================================================== // configure global opengl state // ----------------------------- glEnable(GL_DEPTH_TEST); glEnable(GL_CULL_FACE); // build and compile our shader program [...] // set up vertex data (and buffer(s)) and configure vertex attributes [...] // shader configuration [...] // render loop // =========== while (!glfwWindowShouldClose(window)) { // input processing and fps calculation[...] // render // ------ glClearColor(0.1f, 0.1f, 0.1f, 1.0f); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glDepthMask(GL_TRUE); //enable depth writing glDepthFunc(GL_LEQUAL); //avoid z-fighting //draw ambient component into color and depth buffer view = camera.GetViewMatrix(); projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f); // setting up lighting shader for ambient pass [...] // render the cubes glBindVertexArray(cubeVAO); for (unsigned int i = 0; i < 10; i++) { //position cube [...] glDrawArrays(GL_TRIANGLES, 0, 36); } //------------------------------------------------------------------------------------------------------------------------ glDepthMask(GL_FALSE); //disable depth writing glEnable(GL_BLEND); glBlendFunc(GL_ONE, GL_ONE); //additive blending glEnable(GL_STENCIL_TEST); //setting up shadowShader and lightingShader [...] for (int light = 0; light < lightsused; light++) { glDepthFunc(GL_LESS); glClear(GL_STENCIL_BUFFER_BIT); //configure stencil ops for front- and backface to write according to z-fail glStencilOpSeparate(GL_FRONT, GL_KEEP, GL_DECR_WRAP, GL_KEEP); //-1 for front-facing glStencilOpSeparate(GL_BACK, GL_KEEP, GL_INCR_WRAP, GL_KEEP); //+1 for back-facing glStencilFunc(GL_ALWAYS, 0, GL_TRUE); //stencil test always passes if(hidevolumes) glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE); //disable writing to the color buffer glDisable(GL_CULL_FACE); glEnable(GL_DEPTH_CLAMP); //necessary to render SVs into infinity //draw SV------------------- shadowShader.use(); shadowShader.setInt("lightnr", light); int nr; if (onecaster) nr = 1; else nr = 10; for (int i = 0; i < nr; i++) { //position cube[...] glDrawArrays(GL_TRIANGLES, 0, 36); } //-------------------------- glDisable(GL_DEPTH_CLAMP); glEnable(GL_CULL_FACE); glStencilFunc(GL_EQUAL, 0, GL_TRUE); //stencil test passes for ==0 so only for non shadowed areas glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP); //keep stencil values for illumination glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE); //enable writing to the color buffer glDepthFunc(GL_LEQUAL); //avoid z-fighting //draw diffuse and specular pass lightingShader.use(); lightingShader.setInt("lightnr", light); // render the cubes for (unsigned int i = 0; i < 10; i++) { //position cube[...] glDrawArrays(GL_TRIANGLES, 0, 36); } } glDisable(GL_BLEND); glDepthMask(GL_TRUE); //enable depth writing glDisable(GL_STENCIL_TEST); //------------------------------------------------------------------------------------------------------------------------ // also draw the lamp object(s) [...] // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.) // ------------------------------------------------------------------------------- glfwSwapBuffers(window); glfwP } // optional: de-allocate all resources once they've outlived their purpose: // ------------------------------------------------------------------------ glDeleteVertexArrays(1, &cubeVAO); glDeleteVertexArrays(1, &lightVAO); glDeleteBuffers(1, &VBO); // glfw: terminate, clearing all previously allocated GLFW resources. // ------------------------------------------------------------------ glfwTerminate(); return 0;  
    • By Green_Baron
      i am self teaching me graphics and oo programming and came upon this:
      My Window class creates an input handler instance, the glfw user pointer is redirected to that object and methods there do the input handling for keyboard and mouse. That works. Now as part of the input handling i have an orbiting camera that is controlled by mouse movement. GLFW_CURSOR_DISABLED is set as proposed in the glfw manual. The manual says that in this case the cursor is automagically reset to the window's center. But if i don't reset it manually with glfwSetCursorPos( center ) mouse values seem to add up until the scene is locked up.
      Here are some code snippets, mostly standard from tutorials:
      // EventHandler m_eventHandler = new EventHandler( this, glm::vec3( 0.0f, 5.0f, 0.0f ), glm::vec3( 0.0f, 1.0f, 0.0f ) ); glfwSetWindowUserPointer( m_window, m_eventHandler ); m_eventHandler->setCallbacks(); Creation of the input handler during window creation. For now, the camera is part of the input handler, hence the two vectors (position, up-vector).  In future i'll take that functionally out into an own class that inherits from the event handler.
      void EventHandler::setCallbacks() { glfwSetCursorPosCallback( m_window->getWindow(), cursorPosCallback ); glfwSetKeyCallback( m_window->getWindow(), keyCallback ); glfwSetScrollCallback( m_window->getWindow(), scrollCallback ); glfwSetMouseButtonCallback( m_window->getWindow(), mouseButtonCallback ); } Set callbacks in the input handler.
      // static void EventHandler::cursorPosCallback( GLFWwindow *w, double x, double y ) { EventHandler *c = reinterpret_cast<EventHandler *>( glfwGetWindowUserPointer( w ) ); c->onMouseMove( (float)x, (float)y ); } Example for the cursor pos callback redirection to a class method.
      // virtual void EventHandler::onMouseMove( float x, float y ) { if( x != 0 || y != 0 ) { // @todo cursor should be set automatically, according to doc if( m_window->isCursorDisabled() ) glfwSetCursorPos( m_window->getWindow(), m_center.x, m_center.y ); // switch up/down because its more intuitive m_yaw += m_mouseSensitivity * ( m_center.x - x ); m_pitch += m_mouseSensitivity * ( m_center.y - y ); // to avoid locking if( m_pitch > 89.0f ) m_pitch = 89.0f; if( m_pitch < -89.0f ) m_pitch = -89.0f; // Update Front, Right and Up Vectors updateCameraVectors(); } } // onMouseMove() Mouse movement processor method. The interesting part is the manual reset of the mouse position that made the thing work ...
      // straight line distance between the camera and look at point, here (0,0,0) float distance = glm::length( m_target - m_position ); // Calculate the camera position using the distance and angles float camX = distance * -std::sin( glm::radians( m_yaw ) ) * std::cos( glm::radians( m_pitch) ); float camY = distance * -std::sin( glm::radians( m_pitch) ); float camZ = -distance * std::cos( glm::radians( m_yaw ) ) * std::cos( glm::radians( m_pitch) ); // Set the camera position and perspective vectors m_position = glm::vec3( camX, camY, camZ ); m_front = glm::vec3( 0.0, 0.0, 0.0 ) - m_position; m_up = m_worldUp; m_right = glm::normalize( glm::cross( m_front, m_worldUp ) ); glm::lookAt( m_position, m_front, m_up ); Orbiting camera vectors calculation in updateCameraVectors().
      Now, for my understanding, as the glfw manual explicitly states that if cursor is disabled then it is reset to the center, but my code only works if it is reset manually, i fear i am doing something wrong. It is not world moving (only if there is a world to render :-)), but somehow i am curious what i am missing.
      I am not a professional programmer, just a hobbyist, so it may well be that i got something principally wrong :-)
      And thanks for any hints and so ...
  • Advertisement
  • Popular Now

  • Forum Statistics

    • Total Topics
    • Total Posts

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

Participate in the game development conversation and more when you create an account on GameDev.net!

Sign me up!