Sign in to follow this  

OpenGL Application efficiency in opengl

This topic is 3456 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

Hello every one, I have an application which is written in c++ and opengl and now I want to compare two methods: So, first question that I want to know 1 . how can we know that our funtion is at run time i.e in opengl is this, when the function is interactived with the user ( keyboard or mouse)? or it is used in display function or.... : - 2 . how can I know the speed of this function is this the same of knowing FPS and if it is so how can we compute FPS in opengl, actually I have some ideas about that so for instace we can use this snippet : //----------------------------------------------- // frame rate //------------------------------------------------ frame++; ttime=glutGet(GLUT_ELAPSED_TIME); if (ttime - timebase > 1000) { cout<<s<<"FPS: "<<(frame*1000.0/(ttime-timebase))<<"\n"<<endl; timebase = ttime; frame = 0; } //------------------------------------------------ that could give us the number of frames per second But I still want to know where is the best place in my application to put it, and it says that it gives me the FPS for the etire application when we put it somewhere befor display function call, !!what about only to evaluate one function !! 3 . what is the best number of frames I have got ~ 60 - 75 FPS and I still don't know what is the masurement to be considered during this varying process this FPS increases when we have more goemetry to render or.... 4 . again if this doesn't help for enabling us to evalute the speed of the application .....then ...what do you think. If you have any resources, links, tutorial , ideas to give me a clear clue of efficency of the application I will appreciate any efforts S H E R E E

Share this post

Link to post
Share on other sites
1.) What do you mean with "your function is in opengl"?
2.) looks good
3.) With my very own OpenGL-Framework (Win32, Linux yet to come) and RenderMachine I have about 1500 FPS with no Geometry displayed and minimal code for swapping/clearing the display and a framecounter.
4.) FPS is the most common way to evaluate the Speed. You may use a profiler also (look into Codeblocks, they have a very neat one onboard) which tells you where your bottleneck is.

Share this post

Link to post
Share on other sites
When you use framerate to evaluate the performance of your application, you need to be very careful about what you are talking about.

In general, the framerate measured during the actual rendering is not very useful.

The major problem is came from vsync.

When you do your measurement with vsync on simply, the frame rate will be bounded by the screen refresh rate which is usually 60 Hz (or 75 Hz). So, when you saw a frame rate of 60 Hz, it only represents that your application can run faster than 60 Hz. Not very useful a figure, right?

However, it is not very useful by measuring framerate with vsync off simply neither. When you have vsync off, all function calls to OpenGL become asynchronous. That is just like..., you make a command to someone and return to your own job immediately regardless of the command completed or not. The framerate measured in this case is only reflecting the speed of delivering commands to OpenGL but not the actually loading of the more demanding graphics routines. And so, you can easily write a lousy program but having 2000+ fps.

To measure a more meaningful framerate, you need to turn off vsync, make a call glFinish() at the end of each frame and measure the time to render a number of frames. Of course, you cannot call glFinish() in normal scenario, that's why the framerate measured during the actual rendering is not very useful. (Note that, glFinish() is a synchronous call.)

Just measure the framerate separately and leave it in your documentation. Don't mix it with the actual rendering. Framerate is not an entertaining figure for most people anyway (except the developers), why bother?

[Edited by - ma_hty on August 1, 2008 11:59:11 AM]

Share this post

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

  • Similar Content

    • By xhcao
      Does sync be needed to read texture content after access texture image in compute shader?
      My simple code is as below,
      glBindImageTexture(0, texture[0], 0, GL_FALSE, 3, GL_READ_ONLY, GL_R32UI);
      glBindImageTexture(1, texture[1], 0, GL_FALSE, 4, GL_WRITE_ONLY, GL_R32UI);
      glDispatchCompute(1, 1, 1);
      // Does sync be needed here?
      glBindFramebuffer(GL_READ_FRAMEBUFFER, framebuffer);
                                     GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, texture[1], 0);
      glReadPixels(0, 0, kWidth, kHeight, GL_RED_INTEGER, GL_UNSIGNED_INT, outputValues);
      Compute shader is very simple, imageLoad content from texture[0], and imageStore content to texture[1]. Does need to sync after dispatchCompute?
    • By Jonathan2006
      My question: is it possible to transform multiple angular velocities so that they can be reinserted as one? My research is below:
      // This works quat quaternion1 = GEQuaternionFromAngleRadians(angleRadiansVector1); quat quaternion2 = GEMultiplyQuaternions(quaternion1, GEQuaternionFromAngleRadians(angleRadiansVector2)); quat quaternion3 = GEMultiplyQuaternions(quaternion2, GEQuaternionFromAngleRadians(angleRadiansVector3)); glMultMatrixf(GEMat4FromQuaternion(quaternion3).array); // The first two work fine but not the third. Why? quat quaternion1 = GEQuaternionFromAngleRadians(angleRadiansVector1); vec3 vector1 = GETransformQuaternionAndVector(quaternion1, angularVelocity1); quat quaternion2 = GEQuaternionFromAngleRadians(angleRadiansVector2); vec3 vector2 = GETransformQuaternionAndVector(quaternion2, angularVelocity2); // This doesn't work //quat quaternion3 = GEQuaternionFromAngleRadians(angleRadiansVector3); //vec3 vector3 = GETransformQuaternionAndVector(quaternion3, angularVelocity3); vec3 angleVelocity = GEAddVectors(vector1, vector2); // Does not work: vec3 angleVelocity = GEAddVectors(vector1, GEAddVectors(vector2, vector3)); static vec3 angleRadiansVector; vec3 angularAcceleration = GESetVector(0.0, 0.0, 0.0); // Sending it through one angular velocity later in my motion engine angleVelocity = GEAddVectors(angleVelocity, GEMultiplyVectorAndScalar(angularAcceleration, timeStep)); angleRadiansVector = GEAddVectors(angleRadiansVector, GEMultiplyVectorAndScalar(angleVelocity, timeStep)); glMultMatrixf(GEMat4FromEulerAngle(angleRadiansVector).array); Also how do I combine multiple angularAcceleration variables? Is there an easier way to transform the angular values?
    • By dpadam450
      I have this code below in both my vertex and fragment shader, however when I request glGetUniformLocation("Lights[0].diffuse") or "Lights[0].attenuation", it returns -1. It will only give me a valid uniform location if I actually use the diffuse/attenuation variables in the VERTEX shader. Because I use position in the vertex shader, it always returns a valid uniform location. I've read that I can share uniforms across both vertex and fragment, but I'm confused what this is even compiling to if this is the case.
      #define NUM_LIGHTS 2
      struct Light
          vec3 position;
          vec3 diffuse;
          float attenuation;
      uniform Light Lights[NUM_LIGHTS];
    • By pr033r
      I have a Bachelor project on topic "Implenet 3D Boid's algorithm in OpenGL". All OpenGL issues works fine for me, all rendering etc. But when I started implement the boid's algorithm it was getting worse and worse. I read article ( inspirate from another code (here: but it still doesn't work like in tutorials and videos. For example the main problem: when I apply Cohesion (one of three main laws of boids) it makes some "cycling knot". Second, when some flock touch to another it scary change the coordination or respawn in origin (x: 0, y:0. z:0). Just some streng things. 
      I followed many tutorials, change a try everything but it isn't so smooth, without lags like in another videos. I really need your help. 
      My code (optimalizing branch):
      Exe file (if you want to look) and models folder (for those who will download the sources):
      Thanks for any help...

    • By Andrija
      I am currently trying to implement shadow mapping into my project , but although i can render my depth map to the screen and it looks okay , when i sample it with shadowCoords there is no shadow.
      Here is my light space matrix calculation
      mat4x4 lightViewMatrix; vec3 sun_pos = {SUN_OFFSET * the_sun->direction[0], SUN_OFFSET * the_sun->direction[1], SUN_OFFSET * the_sun->direction[2]}; mat4x4_look_at(lightViewMatrix,sun_pos,player->pos,up); mat4x4_mul(lightSpaceMatrix,lightProjMatrix,lightViewMatrix); I will tweak the values for the size and frustum of the shadow map, but for now i just want to draw shadows around the player position
      the_sun->direction is a normalized vector so i multiply it by a constant to get the position.
      player->pos is the camera position in world space
      the light projection matrix is calculated like this:
      mat4x4_ortho(lightProjMatrix,-SHADOW_FAR,SHADOW_FAR,-SHADOW_FAR,SHADOW_FAR,NEAR,SHADOW_FAR); Shadow vertex shader:
      uniform mat4 light_space_matrix; void main() { gl_Position = light_space_matrix * transfMatrix * vec4(position, 1.0f); } Shadow fragment shader:
      out float fragDepth; void main() { fragDepth = gl_FragCoord.z; } I am using deferred rendering so i have all my world positions in the g_positions buffer
      My shadow calculation in the deferred fragment shader:
      float get_shadow_fac(vec4 light_space_pos) { vec3 shadow_coords = / light_space_pos.w; shadow_coords = shadow_coords * 0.5 + 0.5; float closest_depth = texture(shadow_map, shadow_coords.xy).r; float current_depth = shadow_coords.z; float shadow_fac = 1.0; if(closest_depth < current_depth) shadow_fac = 0.5; return shadow_fac; } I call the function like this:
      get_shadow_fac(light_space_matrix * vec4(position,1.0)); Where position is the value i got from sampling the g_position buffer
      Here is my depth texture (i know it will produce low quality shadows but i just want to get it working for now):
      sorry because of the compression , the black smudges are trees ...
      EDIT: Depth texture attachment:
  • Popular Now