• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
CrHasher

OpenGL
OpenGL VSync stutter issue in main game loop

3 posts in this topic

I’m working on a home project a small graphics engine written in C++11 using GLFW for windowing, but I ran into a vsync related stuttering that I was unable to fix. In the last few weeks I’ve spent countless hours trying to understand what might be wrong in the below game loop but I just can’t figure it out. Even worse is that on a system with Intel HD Graphics 4000 the animation is butter smooth even with vsync Enabled, but on my home PC with nVidia GTX480 I see a lot of animation stutter. sad.pngsad.pngsad.png  ohmy.png
 
Game Loop:

void Engine::run()
{
	if (isRunning_)
		return;

	isRunning_ = true;

	initialize();

	bool vSyncEnabled = window_->getVSyncEnabled();
	
	int frames = 0;
	double frameCounter = 0.0;

	int granularity = 480;

	State current = {};
	current.time.t_ = 0.0;
	current.time.dt_ = 1.0 / granularity;
	current.time.accumulator_ = 0.0;
	
	State previous = current;
	previous.time.start_ = time_->getTime();

	while (isRunning_)
	{
		current.time.start_ = time_->getTime();
		current.time.elapsed_ = current.time.start_ - previous.time.start_;
		previous.time.start_ = current.time.start_;

		if (vSyncEnabled)
			smoothDelta(current.time.elapsed_, granularity);

		if (current.time.elapsed_ > 0.25)
			current.time.elapsed_ = 0.25;

		current.time.accumulator_ += current.time.elapsed_;
		frameCounter += current.time.elapsed_;

		///-- Update
		while (current.time.accumulator_ >= current.time.dt_)
		{
			current.time.accumulator_ -= current.time.dt_;
			previous = current;
			renderManager_->update(current);
			current.time.t_ += current.time.dt_;
		}
		///--

		///-- Render
		renderManager_->interpolate(previous, current);
		renderManager_->render();

		window_->swapBuffers();
		frames++;
		///--

		window_->poolEvents();

		if ( window_->windowShouldClose() )
		{
			stop();
		}
	}

	terminate();
}

Render manager Test Code:

...
void GlRenderManager::update(const State& current)
{
	prevTriangle_ = currTriangle_;

	if ( currTriangle_.x_ >= 0.8 )
		currTriangle_.dir_ = -1;
	if ( currTriangle_.x_ <= -0.8 )
		currTriangle_.dir_ = 1;

	currTriangle_.x_ += currTriangle_.dir_ * current.time.dt_;
}

void GlRenderManager::interpolate(const State& previous, const State& current)
{
	 double alpha = current.time.accumulator_ / current.time.dt_;

	 if (alpha > 0.0)
	 {
		 triangle_.x_ = currTriangle_.x_ * alpha + prevTriangle_.x_ * (1.0 - alpha);
	 }
	 else
	 {
		triangle_ = currTriangle_;
	 }
}

void GlRenderManager::render()
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	GLfloat attrib[] = { (float)triangle_.x_ * 1.0f,
						 0.0f,
						 0.0f,
						 0.0f };

	// Update the value of input attribute 0
	glVertexAttrib4fv(0, attrib);

	glDrawArrays(GL_PATCHES, 0, 3);

	checkErrors(); ///-- Check for OpenGL errors.
}
...

 
Any help would be appreciated rolleyes.gif

0

Share this post


Link to post
Share on other sites

First off, your time handling is quite chaotic smile.png You have a global(?) time state which get manipulated and used in different contexts, eg. your update methods behavior depends on an outer loop where you increase the time. My preferences would be a more clear time management:

	State previous = current;
	previous.time.start_ = time_->getTime();

	while (isRunning_)
	{
                 // update time
		current.time = time_->getTime();
                // update render manager
	        renderManager_->update(current);
		///-- Render
		renderManager_->interpolate(current);
		renderManager_->render();

		window_->swapBuffers();
		frames++;
		///--

		window_->poolEvents();

		if ( window_->windowShouldClose() )
		{
			stop();
		}
	}

Next, let your sub-systems manage its behavior over-time themself. A physic engine will work in a different ways then a render engine or game logic.

...
void GlRenderManager::update(const State& current)
{
       // get render manager previous state
       State& previous = GlRenderManager:: getPreviousUpdateState()

      // time elapse too large ?
      if( (previous.time+MAX_FRAME_TIME)<current.time) {
         previous.time = current.time-MAX_FRAME_TIME;
      }

       // fix your timestep :D 
       while( (previous.time+FIX_TIME_STEP)<current.time) {
   	  prevTriangle_ = currTriangle_;

	  if ( currTriangle_.x_ >= 0.8 )
	  	currTriangle_.dir_ = -1;
  	  if ( currTriangle_.x_ <= -0.8 )
		currTriangle_.dir_ = 1;

	  currTriangle_.x_ += currTriangle_.dir_ * FIX_TIME_STEP;
           previous.time += FIX_TIME_STEP;
      }
}

void GlRenderManager::interpolate(const State& current)
{
       // get render manager previous state
       State& previous = GlRenderManager:: getPreviousUpdateState()

         // works only after update methods has been called
	 double alpha = (current.time-  previous time) / FIX_TIME_STEP;

	 if (alpha > 0.0)
	 {
		 triangle_.x_ = currTriangle_.x_ * alpha + prevTriangle_.x_ * (1.0 - alpha);
	 }
	 else
	 {
		triangle_ = currTriangle_;
	 }
}

void GlRenderManager::render()
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	GLfloat attrib[] = { (float)triangle_.x_ * 1.0f,
						 0.0f,
						 0.0f,
						 0.0f };

	// Update the value of input attribute 0
	glVertexAttrib4fv(0, attrib);

	glDrawArrays(GL_PATCHES, 0, 3);

	checkErrors(); ///-- Check for OpenGL errors.
}
...
0

Share this post


Link to post
Share on other sites

Tried to fix the stutter the way you proposed, moved time management out of the main loop (sort of), but the stutter is even worse now. I have no idea what’s actually wrong. The time step was written based on http://gafferongames.com/game-physics/fix-your-timestep/. And while it works with the downloadable demo project from that site my implementation is behaving strange.

Edited by CrHasher
0

Share this post


Link to post
Share on other sites

Anytime you are dealing with the GPU. If you want to have smooth animation, you need to sync all your animation to vsync, otherwise you will end up with exactly what you are seeing which is micro stuttering. The problem is that your update delta are changing too much between frames and they are not consistent. In DX11 you can DXGI_PRESENT_STATS to get info on whenever vsync happens. I am not sure how you would go about doing that with OpenGL.

0

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0

  • Similar Content

    • By mapra99
      Hello

      I am working on a recent project and I have been learning how to code in C# using OpenGL libraries for some graphics. I have achieved some quite interesting things using TAO Framework writing in Console Applications, creating a GLUT Window. But my problem now is that I need to incorporate the Graphics in a Windows Form so I can relate the objects that I render with some .NET Controls.

      To deal with this problem, I have seen in some forums that it's better to use OpenTK instead of TAO Framework, so I can use the glControl that OpenTK libraries offer. However, I haven't found complete articles, tutorials or source codes that help using the glControl or that may insert me into de OpenTK functions. Would somebody please share in this forum some links or files where I can find good documentation about this topic? Or may I use another library different of OpenTK?

      Thanks!
    • By Solid_Spy
      Hello, I have been working on SH Irradiance map rendering, and I have been using a GLSL pixel shader to render SH irradiance to 2D irradiance maps for my static objects. I already have it working with 9 3D textures so far for the first 9 SH functions.
      In my GLSL shader, I have to send in 9 SH Coefficient 3D Texures that use RGBA8 as a pixel format. RGB being used for the coefficients for red, green, and blue, and the A for checking if the voxel is in use (for the 3D texture solidification shader to prevent bleeding).
      My problem is, I want to knock this number of textures down to something like 4 or 5. Getting even lower would be a godsend. This is because I eventually plan on adding more SH Coefficient 3D Textures for other parts of the game map (such as inside rooms, as opposed to the outside), to circumvent irradiance probe bleeding between rooms separated by walls. I don't want to reach the 32 texture limit too soon. Also, I figure that it would be a LOT faster.
      Is there a way I could, say, store 2 sets of SH Coefficients for 2 SH functions inside a texture with RGBA16 pixels? If so, how would I extract them from inside GLSL? Let me know if you have any suggestions ^^.
    • By KarimIO
      EDIT: I thought this was restricted to Attribute-Created GL contexts, but it isn't, so I rewrote the post.
      Hey guys, whenever I call SwapBuffers(hDC), I get a crash, and I get a "Too many posts were made to a semaphore." from Windows as I call SwapBuffers. What could be the cause of this?
      Update: No crash occurs if I don't draw, just clear and swap.
      static PIXELFORMATDESCRIPTOR pfd = // pfd Tells Windows How We Want Things To Be { sizeof(PIXELFORMATDESCRIPTOR), // Size Of This Pixel Format Descriptor 1, // Version Number PFD_DRAW_TO_WINDOW | // Format Must Support Window PFD_SUPPORT_OPENGL | // Format Must Support OpenGL PFD_DOUBLEBUFFER, // Must Support Double Buffering PFD_TYPE_RGBA, // Request An RGBA Format 32, // Select Our Color Depth 0, 0, 0, 0, 0, 0, // Color Bits Ignored 0, // No Alpha Buffer 0, // Shift Bit Ignored 0, // No Accumulation Buffer 0, 0, 0, 0, // Accumulation Bits Ignored 24, // 24Bit Z-Buffer (Depth Buffer) 0, // No Stencil Buffer 0, // No Auxiliary Buffer PFD_MAIN_PLANE, // Main Drawing Layer 0, // Reserved 0, 0, 0 // Layer Masks Ignored }; if (!(hDC = GetDC(windowHandle))) return false; unsigned int PixelFormat; if (!(PixelFormat = ChoosePixelFormat(hDC, &pfd))) return false; if (!SetPixelFormat(hDC, PixelFormat, &pfd)) return false; hRC = wglCreateContext(hDC); if (!hRC) { std::cout << "wglCreateContext Failed!\n"; return false; } if (wglMakeCurrent(hDC, hRC) == NULL) { std::cout << "Make Context Current Second Failed!\n"; return false; } ... // OGL Buffer Initialization glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT); glBindVertexArray(vao); glUseProgram(myprogram); glDrawElements(GL_TRIANGLES, indexCount, GL_UNSIGNED_SHORT, (void *)indexStart); SwapBuffers(GetDC(window_handle));  
    • By Tchom
      Hey devs!
       
      I've been working on a OpenGL ES 2.0 android engine and I have begun implementing some simple (point) lighting. I had something fairly simple working, so I tried to get fancy and added color-tinting light. And it works great... with only one or two lights. Any more than that, the application drops about 15 frames per light added (my ideal is at least 4 or 5). I know implementing lighting is expensive, I just didn't think it was that expensive. I'm fairly new to the world of OpenGL and GLSL, so there is a good chance I've written some crappy shader code. If anyone had any feedback or tips on how I can optimize this code, please let me know.
       
      Vertex Shader
      uniform mat4 u_MVPMatrix; uniform mat4 u_MVMatrix; attribute vec4 a_Position; attribute vec3 a_Normal; attribute vec2 a_TexCoordinate; varying vec3 v_Position; varying vec3 v_Normal; varying vec2 v_TexCoordinate; void main() { v_Position = vec3(u_MVMatrix * a_Position); v_TexCoordinate = a_TexCoordinate; v_Normal = vec3(u_MVMatrix * vec4(a_Normal, 0.0)); gl_Position = u_MVPMatrix * a_Position; } Fragment Shader
      precision mediump float; uniform vec4 u_LightPos["+numLights+"]; uniform vec4 u_LightColours["+numLights+"]; uniform float u_LightPower["+numLights+"]; uniform sampler2D u_Texture; varying vec3 v_Position; varying vec3 v_Normal; varying vec2 v_TexCoordinate; void main() { gl_FragColor = (texture2D(u_Texture, v_TexCoordinate)); float diffuse = 0.0; vec4 colourSum = vec4(1.0); for (int i = 0; i < "+numLights+"; i++) { vec3 toPointLight = vec3(u_LightPos[i]); float distance = length(toPointLight - v_Position); vec3 lightVector = normalize(toPointLight - v_Position); float diffuseDiff = 0.0; // The diffuse difference contributed from current light diffuseDiff = max(dot(v_Normal, lightVector), 0.0); diffuseDiff = diffuseDiff * (1.0 / (1.0 + ((1.0-u_LightPower[i])* distance * distance))); //Determine attenuatio diffuse += diffuseDiff; gl_FragColor.rgb *= vec3(1.0) / ((vec3(1.0) + ((vec3(1.0) - vec3(u_LightColours[i]))*diffuseDiff))); //The expensive part } diffuse += 0.1; //Add ambient light gl_FragColor.rgb *= diffuse; } Am I making any rookie mistakes? Or am I just being unrealistic about what I can do? Thanks in advance
    • By yahiko00
      Hi,
      Not sure to post at the right place, if not, please forgive me...
      For a game project I am working on, I would like to implement a 2D starfield as a background.
      I do not want to deal with static tiles, since I plan to slowly animate the starfield. So, I am trying to figure out how to generate a random starfield for the entire map.
      I feel that using a uniform distribution for the stars will not do the trick. Instead I would like something similar to the screenshot below, taken from the game Star Wars: Empire At War (all credits to Lucasfilm, Disney, and so on...).

      Is there someone who could have an idea of a distribution which could result in such a starfield?
      Any insight would be appreciated
  • Popular Now