• 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
Prot

OpenGL
How to react on KeyPress + Release?

7 posts in this topic

Hi I followed the tutorial on Swiftless. The last post I worked through was about Keyboard input and it does work. Basically what he covers is how to detect whether a key was pressed or realeased.

 

So I tried to experiment around. To do so I wanted to make the application to terminate when 'e' is pressed.

#include "glew.h"// Include the GLUT header file  
#include "glut.h" // Include the GLEW header file  

bool* keyStates = new bool[256](); // Create an array of boolean values of length 256 (0-255)
bool* keySpecialStates = new bool[256](); // Create an array of boolean values of length 256 (0-255)
bool* keyPreviousStates = new bool[256]();


void renderPrimitive(void)
{
	glBegin(GL_QUADS); // Start drawing a quad primitive
	glVertex3f(-1.0f,-1.0f,0.0f); //Bottom Left
	glVertex3f(-1.0f,1.0f,0.0f); //Top Left
	glVertex3f(1.0f,1.0f,0.0f); //Top Right
	glVertex3f(1.0f,-1.0f,0.0f); //Bottom Right
	glEnd();
}

void keyOperations(void)
{
	if ((!keyStates['e']) && keyPreviousStates['e']) // If the 'a' key has been pressed 
	{
		// Perform 'e' key operations
		exit(0);
	}
}

void keySpecialOperations(void)
{
	if (keySpecialStates[GLUT_KEY_LEFT]) // If the left arrow key has been pressed
	{
		// Perform left arrow key operations
	}
}

void display(void) {
	keyOperations();
	keySpecialOperations();
	glClearColor(0.706f, 0.706f, 0.706f, 2.0f); // Clear the background of our window to red  
	glClear(GL_COLOR_BUFFER_BIT); //Clear the colour buffer (more buffers later on)  
	glLoadIdentity(); // Load the Identity Matrix to reset our drawing locations  

	glTranslatef(0.0f,0.0f,-5.0f); // Push eveything 5 units back into the scene, otherwise we won't see the primitive
	renderPrimitive(); //render the primitive
	glFlush(); // Flush the OpenGL buffers to the window  
	keyPreviousStates = keyStates;
}

void reshape(int width, int height)
{
	glViewport(0, 0, (GLsizei)width, (GLsizei)height); // Set our viewport to the size of our window. (0,0) being bottom left in the window.
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity(); // Reset the projection matrix to the identity matrix so that we don't get any artifacts (cleaning up)
	gluPerspective(60,(GLfloat)width/(GLfloat)height,1.0,100.0); // Set the Field of view angle (in degrees), the aspect ratio of our window, and the new and far planes
	glMatrixMode(GL_MODELVIEW);
}

void keyPressed(unsigned char key,int x, int y)
{
	keyStates[key] = true; //Set the state of the current key to pressed	
}

void keyUp(unsigned char key,int x, int y)
{
	keyStates[key] = false; //Set the state of the current key to not pressed
}

void keySpecial(int key, int x,int y)
{
	keySpecialStates[key] = true;
}

void keySpecialUp(int key,int x,int y)
{
	keySpecialStates[key] = false;
}

int main(int argc, char **argv) {
	glutInit(&argc, argv); // Initialize GLUT  
	glutInitDisplayMode(GLUT_SINGLE); // Set up a basic display buffer (only single buffered for now)  
	glutInitWindowSize(500, 500); // Set the width and height of the window  
	glutInitWindowPosition(100, 100); // Set the position of the window  
	glutCreateWindow("Your first OpenGL Window"); // Set the title for the window  

	glutDisplayFunc(display); // Tell GLUT to use the method "display" for rendering  
	glutReshapeFunc(reshape); // Tell GLUT to use the method "reshape" for reshaping
	glutKeyboardFunc(keyPressed); // Tell GLUT to use the method "keyPressed" for key presses 
	glutKeyboardUpFunc(keyUp); // Tell GLUT to use the method "keyUp" for key up events  
	glutSpecialFunc(keySpecial); // Tell GLUT to use the method "keySpecial" for special key presses
	glutSpecialUpFunc(keySpecialUp); // Tell GLUT to use the method "keySpecialUp" for special up key events

	glutMainLoop(); // Enter GLUT's main loop  
}

So I changed the keyOperations() code a little. I tried to add another bool-array which stores the state of the keys from the previous display()-iteration. Then I try to check if 'e' is currently released and if its previous state was pressed. But nothing happens smile.png

 

I guess this a very basic thing but I am very new to OpenGL and C++ so I could only think of the way I would implement this in XNA. Btw I am assigning the previous key states at the end of the display function.

 

Thanks in advance.

Edited by Prot
0

Share this post


Link to post
Share on other sites

After the first run through display() both keyStates and keyPreviousState point to the same memory area. You probably want to use memcpy to copy the memory area pointed to by keyStates to the memory area pointed to by keyPreviousStates, but actually you copy the pointer keyStates to keyPreviousStates.

 

EDIT: To avoid such problems and clearly denote the situation, you should use const to make the variables read-only, in this case

bool* const keyStates = new bool[256]();
bool* const keyPreviousStates = new bool[256]();

Notice that this does not make the array elements read-only but just the pointers themselves.

Edited by haegarr
2

Share this post


Link to post
Share on other sites

After the first run through display() both keyStates and keyPreviousState point to the same memory area. You probably want to use memcpy to copy the memory area pointed to by keyStates to the memory area pointed to by keyPreviousStates, but actually you copy the pointer keyStates to keyPreviousStates.

 

EDIT: To avoid such problems and clearly denote the situation, you should use const to make the variables read-only, in this case

bool* const keyStates = new bool[256]();
bool* const keyPreviousStates = new bool[256]();

Notice that this does not make the array elements read-only but just the pointers themselves.

 

So now I declared the pointers as constants and tried the following in order to cpoy the actual array:

memcpy(keyPreviousStates,keyStates, sizeof(keyStates));

Also tried:

memcpy(keyPreviousStates,keyStates, 256 * sizeof(bool));

It still does not work. Any suggestions?

Edited by Prot
0

Share this post


Link to post
Share on other sites

Is the display routine invoked regularly at all? Set a breakpoint into the display() routine and look what happens.

 

Yes it is, otherwise it would not draw anything I guess. But while stepping through the method something strange happened. When the debugger hit the memcpy() line it VS opened a OpenFileDialog and said that it was missing a memcpy.asm file.

 

What does that mean it didn't throw any errors when compiling without breakpoints.

0

Share this post


Link to post
Share on other sites

 

Is the display routine invoked regularly at all? Set a breakpoint into the display() routine and look what happens.

 
Yes it is, otherwise it would not draw anything I guess.

 

There's between being called once and being called regularly. GLUT will only issue a call to the display function when the contents is invalidated which typically happens when for example, the window is created, the window is resized, or when the window is moved behind other windows. Otherwise, the display callback is not called again unless you explicitly force a redisplay.

 

So, your display function is called once which explains why something is rendered, but not regularly which explains why nothing more is happening after that. You need to use the idle callback to keep the program busy all the time instead of idling when there's nothing new to display.

 

Quick solution:

void idle()
{
    glutPostRedisplay();
}
 
int main()
{
    ...
    glutIdleCallback(idle);
    glutMainLoop();
}
As soon as there's nothing else for GLUT to do, it calls the idle callback which then forces GLUT to redraw the window.
 
 

But while stepping through the method something strange happened. When the debugger hit the memcpy() line it VS opened a OpenFileDialog and said that it was missing a memcpy.asm file.
 
What does that mean it didn't throw any errors when compiling without breakpoints.

You're stepping into the memcpy call but the debugger can't find the source for the memcpy function. Could be that the source directories are not set up properly or you haven't installed the runtime library source. Quick solution is to step over the call, and into it.

2

Share this post


Link to post
Share on other sites


There's between being called once and being called regularly. GLUT will only issue a call to the display function when the contents is invalidated which typically happens when for example, the window is created, the window is resized, or when the window is moved behind other windows. Otherwise, the display callback is not called again unless you explicitly force a redisplay.



So, your display function is called once which explains why something is rendered, but not regularly which explains why nothing more is happening after that. You need to use the idle callback to keep the program busy all the time instead of idling when there's nothing new to display.



Quick solution:

void idle()
{
glutPostRedisplay();
}

int main()
{
...
glutIdleCallback(idle);
glutMainLoop();
}
As soon as there's nothing else for GLUT to do, it calls the idle callback which then forces GLUT to redraw the window.

 

Hey this advice did the job! Maybe two more things I noticed here:

 

  1. I implemented a concole application which copied one array to another under the very same circumstances and it did work.
  2. I had to assign the idle()-function using glutIdleFunc() not glutIdleCallback() (this one wasn't even suggested by VS).

But now it works thanks a lot. You were right coming from XNA I assumed that display here would be somehow similar to the Draw() function which is called in regular intervals.

0

Share this post


Link to post
Share on other sites

I had to assign the idle()-function using glutIdleFunc() not glutIdleCallback() (this one wasn't even suggested by VS).

 

My mistake, glutIdleFunc is of course correct.

1

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 fllwr0491
      I googled around but are unable to find source code or details of implementation.
      What keywords should I search for this topic?
      Things I would like to know:
      A. How to ensure that partially covered pixels are rasterized?
         Apparently by expanding each triangle by 1 pixel or so, rasterization problem is almost solved.
         But it will result in an unindexable triangle list without tons of overlaps. Will it incur a large performance penalty?
      B. A-buffer like bitmask needs a read-modiry-write operation.
         How to ensure proper synchronizations in GLSL?
         GLSL seems to only allow int32 atomics on image.
      C. Is there some simple ways to estimate coverage on-the-fly?
         In case I am to draw 2D shapes onto an exisitng target:
         1. A multi-pass whatever-buffer seems overkill.
         2. Multisampling could cost a lot memory though all I need is better coverage.
            Besides, I have to blit twice, if draw target is not multisampled.
       
    • 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
  • Popular Now