Jump to content
  • Advertisement
Sign in to follow this  

OpenGL Rendering Quake III BSP In DirectX

This topic is 5028 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

Hey, I've been reading a load of documentation lately on Quake III's BSP format as well as a number of tutorials, namely the one's from GameTutorials.com in which the writer goes through loading the base level to lightmaps and utilizing nodes and leaves. The one question that is nagging at the back of my mind is how to go about rendering the level face by face. I know in OpenGL there is no such think as a "vertex buffer" and thus they can use glDrawArrays quite easily without a decline in performance. In DirectX on the other hand I know of no way of drawing a number of texture mapped primitives without having a vertex buffer with at least 3 vertices assigned to it. I think what I'm looking at here is having to use a dynamic vertex buffer and as I loop through each "face" from the BSP file, I populate the vertex buffer, set the textures (normal and lightmap), set any lights and then render it, continually looping through each face until I reach the end. From looking at this I believe this should stop the video card from locking during rendering as it will be rendering a group of vertices while I'm buidling up the next face. for( int i = 0; i < numFaces; i++ ) { lock the buffer populate the buffer with faces[ i ]; set the texture at texture[ faces->texturID ]; set the stream source and everything drawprimitive } If anyone else has any other experience with this it'd be great if you could provide me with some insight of whether or not this is how you went about rendering the level, and if not, what is the best solution here? Thanks in advance, Permafried-

Share this post

Link to post
Share on other sites
The method you propose is *definetly* not DirectX friendly. Locking the vertex buffer and calling DrawPrimitive() for each face is going to kill your application.

According to this slideset (which I consider reliable), you only get about 25,000 DrawPrimitive() calls per second. You could very easily go over 25,000 DrawPrimitive() calls per frame.

Also, you shouldn't be locking many vertex buffer per frame. Locking a vertex buffer or index buffer causes a windows mode transition, from user mode to kernel mode (and back). This is to be avoided, or at least kept to a minimum.

I'm not familiar with Quake III BSP, but would it be possible to put all of the visible triangles into a vertex buffer, and make one DP call? Like:
Lock the buffer

for each rendered face
add vertices

Unlock the vertex buffer

Set texture
Set stream source

However, you probably have a lot of different textures visible at one time. If possible, minimize the number of textures, because each requires another SetTexture() and DrawPrimitive(). You could still only make one Lock(), if you do it like this:
Lock the buffer

for each texture n
for each rendered face with texture n
add vertices

add vertex offset to offsetList

Unlock the buffer

for each offset in offsetList
SetStreamSource with offset

Share this post

Link to post
Share on other sites

Thanks for the reply. I know that rendering my level in this way is definitely not DirectX friendly but the problem arises, as you mentioned, having multiple textures where each face has not only a graphical texture assigned to it but a lightmap as well. This means that for each x number of vertices, I need to render just that subset and the texture assigned to it. This is where loading in and utilizing the Quake III .BSP format's PVS data will come in handy.

A thorough explanation of Quake III .BSP formats can be found at:
Game Tutorials

There are also 3 tutorials which build upon one another from loading and rendering the raw vertices to implementing the BSP tree and PVS.

I'm still going to be using a dynamic vertex buffer and populating it every frame with the PVS (I guess I could do a check and if it hasn't changed, don't update it ^_^) but looping through in this way should hopefully help to improve my performance.

Thanks again, I'll keep your suggestions in mind when I go back to optimizing this evening. My first goal is to simply get the level rendering in which case the architecture mentioned above should easily port over from raw rendering to selective rendering. Let me know if this seems to make a little more sense and I'm on the right track based on what you suggested.


Share this post

Link to post
Share on other sites
I have been working on a Quake 3 renderer lately and Dustin is correct. You need to sort the faces by texture and then add them to the vertex/index buffer. Make sure when you create your vertex and index buffers that you use the dynamic creation flag and also when you lock them you want to use the discard flag.

Share this post

Link to post
Share on other sites

I was wondering if you'd had any success to this point getting your level to render correctly or not. I know that Quake III uses triangle fans to render, but my biggest problem right now is figuring out the number of primitives to render based on the number of vertices contained within the face.

I created a normal vertex buffer for the sake of attempting to render the entire thing, but no matter what I've tried I can't get the thing to display, though I'm almost 100% sure it's loading correctly as I've gotten all the required information including vertices, faces and textures to this point.

When I load the level I've populated the vertex buffer and loaded all of the textures and have tried looping through the faces and rendeirng them using:

pd3dDevice->SetFVF( CLevel::dwFVF );
pd3dDevice->SetStreamSource( 0, m_pvbVertexLevelVertexBuffer, 0, sizeof( CLevelVertex ) );
pd3dDevice->SetTexture( 0, m_pFaces[ i ]->textureID );
DrawPrimitive( D3DPT_TRIANGLEFAN, m_pFaces[ i ]->startVertex, ?!? );

For the time being, I really shouldn't have to worry about the offset into my vertex buffer as each face cotains the offset into the BSPVertex array which would correspond to the vertex buffer's offset as i copy vertex by vertex. Any help here would be appreciated as I'm a little confused oh why this thing just won't render.

Thanks again,


Share this post

Link to post
Share on other sites
That seems to be the correct method.
I would also add that you should be using an index buffer and use the indices for each face too.
What you are doing should, in theory, work.
Try putting using the debug DirectX library on the highest output level and your output window in Visual Studio should give you some clues as to what the problem is.

Share this post

Link to post
Share on other sites
I think one of the major problems is rendering using triangle fans as Quake III did, but DirectX has the limitation that you have to provide any drawing method with the number of primitives, and there is no nice way as far as I can see to calculate the number of triangle fans based on the number of vertices to be drawn. I have a feeling if I could resolve this number correctly and mess with my rendering a little bit more I should be on the right track.

Any ideas on this?

Another thing I found, which is incredibly strange....I dumped out the vertices as they were loaded from my application and the last 15 vertices are churning out absolute garbage. I compared this with the dump from the OpenGL tutorial I've been using as a guide and my code looks identical as far as I can tell. I am getting back the correct number of vertices, faces and textures, but my vertices aren't loading correctly after the 52nd one. Here's what I've got as far as loading vertices:

struct tBSPVertex
D3DXVECTOR3 d3dvOrigin; ///< The position of the vertex in 3D space
D3DXVECTOR2 d3dvTexCoords; ///< The texture coordinates of this vertex's texture
D3DXVECTOR2 d3dvTexLightMap; ///< The texture coordinates of this vertex's lightmap
D3DXVECTOR3 d3dvNormal; ///< The normal calculated for this vertex
unsigned char ucColour[ 4 ]; ///< The colour of this vertex

bool CLevel::levelLoadLevel( char* szLevel )
// get the total number of vertices
m_iNumOfVertices = bspLumps[ LUMP_VERTICES ].iLength / sizeof( tBSPVertex );

// allocate memory for the vertices to be read in
m_pVertices = new tBSPVertex[ m_iNumOfVertices ];

// seek to the position in the file which contains the vertices
fseek( pFile, bspLumps[ LUMP_VERTICES ].iOffset, SEEK_SET );

// loop through all the vertices and populate the vertex array
for( int i = 0; i < m_iNumOfVertices; i++ )
// read in the current vertex
fread( &m_pVertices[ i ], 1, sizeof( tBSPVertex ), pFile );

// reverse the positional coords, quake III uses Z as up
float fTemp = m_pVertices[ i ].d3dvOrigin.y;
m_pVertices[ i ].d3dvOrigin.y = m_pVertices[ i ].d3dvOrigin.z;
m_pVertices[ i ].d3dvOrigin.z = -fTemp;

// negate the textures coords otherwise it'll be upside down
m_pVertices[ i ].d3dvTexCoords.y *= -1;

I've also tried without swapping the y and z and I can manage to get to vertex 70 before it barfs..I'm totally lost on this one, I can see nothing wrong with my code above nor the level load itself....hopefully a fresh set of eyes will help ^_^.

Thanks again for all your help,


[Edited by - Permafried- on August 17, 2004 9:28:31 PM]

Share this post

Link to post
Share on other sites
What flags are you opening your file with? I recently had a problem just like this. The solution was to open it read-binary flag:

file = fopen( filename, "rb" );

Also, you may just want to try something to see if it makes a difference:

fseek( pFile, bspLumps[ LUMP_VERTICES ].iOffset, SEEK_SET );
fread( (void*)m_pVertices, m_iNumOfVertices, sizeof( tBSPVertex ), pFile );

// loop through all the vertices and populate the vertex array
for( int i = 0; i < m_iNumOfVertices; i++ )
// reverse the positional coords, quake III uses Z as up
float fTemp = m_pVertices[ i ].d3dvOrigin.y;
m_pVertices[ i ].d3dvOrigin.y = m_pVertices[ i ].d3dvOrigin.z;
m_pVertices[ i ].d3dvOrigin.z = -fTemp;

// negate the textures coords otherwise it'll be upside down
m_pVertices[ i ].d3dvTexCoords.y *= -1;

Share this post

Link to post
Share on other sites

I can't believe after all that trouble of disappearing vertices when loading that it was that simple little b....and of course while going through line after line of code that is something more than easy enough to miss.

Thanks a lot that solved the problem, I now have all the vertices in the exact order and format that the tutorial does, so hopefully tomorrow I can tackle the issue of rendering.

In regards to rendering, if I'm not mistaken the number of primitives on a DrawPrimitive call when using triangle fans should be ( number of vertices - 2 ), this seems to stay true in all cases even though I haven't tried it in code yet.

Thanks again,


[Edited by - Permafried- on August 18, 2004 11:47:52 AM]

Share this post

Link to post
Share on other sites
Hello again,

Well I finally got the geometry rendering, but noticed my textures were completely whack. I created a quick file output routine to check all the information about the vertex and noticed the texture coords are right outta whack (ignore the - this is due to a dumb calculation I had in the code):

Face: 0
Start Vert: 0
Num Verts: 6
Vertex 0: -128 264 64 0 -4
Vertex 1: -128 264 -64 0 -2
Vertex 2: 0 264 -184 2 -0.125
Vertex 3: 184 264 -184 4.875 -0.125
Vertex 4: 184 264 184 4.875 -5.875
Vertex 5: -128 264 184 0 -5.875
Texture: 0

Face: 1
Start Vert: 6
Num Verts: 5
Vertex 6: -128 264 184 2 -5.875
Vertex 7: 184 264 184 6.875 -5.875
Vertex 8: 184 632 184 6.875 -0.125
Vertex 9: -248 632 184 0.125 -0.125
Vertex 10: -248 384 184 0.125 -4
Texture: 0

Face: 2
Start Vert: 11
Num Verts: 4
Vertex 11: 184 264 184 0.125 -5.875
Vertex 12: 184 264 -184 5.875 -5.875
Vertex 13: 184 632 -184 5.875 -0.125
Vertex 14: 184 632 184 0.125 -0.125
Texture: 0

Face: 3
Start Vert: 15
Num Verts: 5
Vertex 15: -248 632 -184 0.125 -0.125
Vertex 16: 184 632 -184 6.875 -0.125
Vertex 17: 184 264 -184 6.875 -5.875
Vertex 18: 0 264 -184 4 -5.875
Vertex 19: -248 320 -184 0.125 -5
Texture: 0

Face: 4
Start Vert: 20
Num Verts: 5
Vertex 20: -248 632 184 0.125 -0.125
Vertex 21: -248 632 -184 5.875 -0.125
Vertex 22: -248 320 -184 5.875 -5
Vertex 23: -248 320 -64 4 -5
Vertex 24: -248 384 184 0.125 -4
Texture: 0

Face: 5
Start Vert: 25
Num Verts: 4
Vertex 25: -248 632 184 0.125 -5.875
Vertex 26: 184 632 184 6.875 -5.875
Vertex 27: 184 632 -184 6.875 -0.125
Vertex 28: -248 632 -184 0.125 -0.125
Texture: 0

Face: 6
Start Vert: 29
Num Verts: 4
Vertex 29: -128 384 64 0.5 0
Vertex 30: -128 320 -64 1.5 -0.5
Vertex 31: -128 264 -64 1.5 -0.9375
Vertex 32: -128 264 64 0.5 -0.9375
Texture: 1

Face: 7
Start Vert: 33
Num Verts: 4
Vertex 33: -248 384 64 0.0625 -1.5
Vertex 34: -248 320 -64 0.0625 -0.5
Vertex 35: -128 320 -64 1 -0.5
Vertex 36: -128 384 64 1 -1.5
Texture: 1

Face: 8
Start Vert: 37
Num Verts: 4
Vertex 37: -128 320 -64 1 -1.5
Vertex 38: -248 320 -64 0.0625 -1.5
Vertex 39: -248 320 -184 0.0625 -0.5625
Vertex 40: -128 320 -184 1 -0.5625
Texture: 1

Face: 9
Start Vert: 41
Num Verts: 4
Vertex 41: 0 264 -184 1.4375 -0.9375
Vertex 42: 0 264 -64 0.5 -0.9375
Vertex 43: 0 272 -64 0.5 -0.875
Vertex 44: 0 272 -184 1.4375 -0.875
Texture: 1

Face: 10
Start Vert: 45
Num Verts: 4
Vertex 45: 0 264 -64 1 -0.9375
Vertex 46: -128 264 -64 0 -0.9375
Vertex 47: -128 320 -64 0 -0.5
Vertex 48: 0 272 -64 1 -0.875
Texture: 1

Face: 11
Start Vert: 49
Num Verts: 4
Vertex 49: -128 320 -184 0 -0.5625
Vertex 50: 0 272 -184 1 -0.5625
Vertex 51: 0 272 -64 1 -1.5
Vertex 52: -128 320 -64 0 -1.5
Texture: 1

Face: 12
Start Vert: 53
Num Verts: 4
Vertex 53: -128 264 64 1.5 -0.9375
Vertex 54: -128 264 184 0.5625 -0.9375
Vertex 55: -128 384 184 0.5625 0
Vertex 56: -128 384 64 1.5 0
Texture: 1

Face: 13
Start Vert: 57
Num Verts: 4
Vertex 57: -128 384 184 1 -1.4375
Vertex 58: -248 384 184 0.0625 -1.4375
Vertex 59: -248 384 64 0.0625 -0.5
Vertex 60: -128 384 64 1 -0.5
Texture: 1

Face: 14
Start Vert: 61
Num Verts: 4
Vertex 61: 40 320 184 0.5625 -0.5
Vertex 62: 40 320 88 1.3125 -0.5
Vertex 63: 40 336 88 1.3125 -0.375
Vertex 64: 40 336 184 0.5625 -0.375
Texture: 1

Face: 15
Start Vert: 65
Num Verts: 4
Vertex 65: 40 320 88 0.3125 -0.5
Vertex 66: 184 320 88 1.4375 -0.5
Vertex 67: 184 336 88 1.4375 -0.375
Vertex 68: 40 336 88 0.3125 -0.375
Texture: 1

Face: 16
Start Vert: 69
Num Verts: 4
Vertex 69: 184 320 88 1.4375 -0.6875
Vertex 70: 40 320 88 0.3125 -0.6875
Vertex 71: 40 320 184 0.3125 -1.4375
Vertex 72: 184 320 184 1.4375 -1.4375
Texture: 1

Face: 17
Start Vert: 73
Num Verts: 4
Vertex 73: 40 336 184 0.3125 -1.4375
Vertex 74: 40 336 88 0.3125 -0.6875
Vertex 75: 184 336 88 1.4375 -0.6875
Vertex 76: 184 336 184 1.4375 -1.4375
Texture: 1

The last two digits are the texture coordinates and I've never seen texture coords of 4.0 in my life. Is there any way to make DirectX recognize this or am I basically SOL for rendering with these kinds of numbers?

Thanks again,


PS: Yzzid, if you happen to come across this post again, have you ever run across this when rendering using ur Quake III BSP renderer or is something else maybe the problem here?

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!