• 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
Wh0p

OpenGL
Simple multiple textures

4 posts in this topic

I did D3D for a "long" time now and am somewhat new to OpenGL (still at the basics)

 

What i am trying to do is:

... Initialize

> Load texture1, Load texture2

... Render

> Bind texture1 to texture unit 0, render some geometry

> Bind texture2 to texture unit 0, render some geometry

 

In short it doenst work as expected. The result is, that both geometry is rendered with texture2 on it. So i looked up the docs and they were stating:

"glTexSubImage2D specifies a two-dimensional subtexture for the current texture unit, specified with glActiveTexture."

 

So I spent some time on trial and erroring around and finally I activated texture unit 1 before loading texture 2 which yields the correct result if I bind at rendering texture1 to tex unit 0 and texture2 to tex uint 1. Binding both textures to tex unit 0 will render the geometry only with texture1.

Actually this feels like the instand I call glTexImage* when having bound a texture to a certain tex uint (texture2 at 0) the the data I loaded before that (texture1 at 0) gets discarded?

 

I'm not quite sure what that would mean. Is it ture, that I need to spend a tex uint for each texture??? I cannot believe that, this would suggest that my graphics card has a 96 (GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS) textures max limit (no way). 

 

so here some snippets on how I (initially inteded to) do the loading and rendereing (both geometry gets rendered with texture2 on it):

glGenTextures (1, &tex);
glBindTexture (cfg.GetBindFlag (), tex);
glTexStorage2D(tex, cfg.GetMipLevel (), cfg.GetTextureFormat (), cfg.GetWidth (), cfg.GetHeight ());
glTexImage2D (cfg.GetBindFlag (), 
	cfg.GetMipLevel (), 
	cfg.GetTextureFormat (), 
	cfg.GetWidth (), cfg.GetHeight (), 0, 
	cfg.GetDataFormat (), 
	cfg.GetDataType (), initdata);
glActiveTexture (_TexUnit); // _TexUnit is asserted as GL_TEXTURE0 + _TexUnitIndex
glBindTexture (resource->GetBindFlag (), resource->GetGLID ()); // resource::_GLID is corresponds to names of texture1 and texture 2
glUniform1i (_Location, _TexUnitIndex); // _Location is the uniform sampler bindpoint in the shader, _TexUnitIndex is 0 in both rendering events
_Sampler->Bind (_TexUnitIndex);

I actually conclude that I have to have missed something, the question is what? Hopefully some of you can point me a diretion.

0

Share this post


Link to post
Share on other sites

Ok, so I publically denounced myself... it was a "variable not initialized error" which took me 1 and a half day to track down and of cource I posted here 2 hours befor i finally found the error....

 

But anyways, i would be glad of some explanation to the documentation. What does that "specifies a two-dimensional subtexture for the current texture unit" mean? Why is the texture unit relevant in the context of uploading texture data?

0

Share this post


Link to post
Share on other sites

 
But anyways, i would be glad of some explanation to the documentation. What does that "specifies a two-dimensional subtexture for the current texture unit" mean?

glTexSubImage, and equivalent for the other Sub-variants, modifies as sub-rectangle of an existing texture. Say you have a 128x128-pixel texture consisting of a 4x4 grid of 32x32-pixel tiles. You can use it to update/replace a single tile without having to upload an entirely new texture image.

Why is the texture unit relevant in the context of uploading texture data?

OpenGL has a bind-to-edit model which means you have to bind the texture object to make it the currently active object. Subsequent calls to glTexImage and such then operates on the currently bound texture. As you may have noticed, you never tell glTexImage which texture object to populate with texture data; that is given from the previous call to glBindTexture.

 

Since multitexturing allows for multiple textures to be bound at the same time, the texture bound to the currently active texture unit is the target of glTexImage.

Edited by Brother Bob
1

Share this post


Link to post
Share on other sites

I'm sorry to say that but you just pointed out the obvisous for me :P

 


you never tell glTexImage which texture object to populate with texture data

 

Yes of course. What I was actually wondering, is why the docs refer to the texture unit and especially glActiveTexture.

I thought glActiveTexture, should have nothing to do with what is stored in the texture but instead is a mechanism to access the texture via glsl.

0

Share this post


Link to post
Share on other sites

The glTexImage function doesn't have a parameter specifying which texture unit to store the data to, so the documentation tells you it will store the data to the current texture unit. The way to specify the current texture unit is glActiveTexture.

 

To get the texture in GLSL, you need to use a sampler and make it available to your shader program.

 

Edit: this is the same thing Brother Bob said, but hopefully if a few people tell you the same thing in different ways it will click.

Edited by richardurich
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 Toastmastern
      So it's been a while since I took a break from my whole creating a planet in DX11. Last time around I got stuck on fixing a nice LOD.
      A week back or so I got help to find this:
      https://github.com/sp4cerat/Planet-LOD
      In general this is what I'm trying to recreate in DX11, he that made that planet LOD uses OpenGL but that is a minor issue and something I can solve. But I have a question regarding the code
      He gets the position using this row
      vec4d pos = b.var.vec4d["position"]; Which is then used further down when he sends the variable "center" into the drawing function:
      if (pos.len() < 1) pos.norm(); world::draw(vec3d(pos.x, pos.y, pos.z));  
      Inside the draw function this happens:
      draw_recursive(p3[0], p3[1], p3[2], center); Basically the 3 vertices of the triangle and the center of details that he sent as a parameter earlier: vec3d(pos.x, pos.y, pos.z)
      Now onto my real question, he does vec3d edge_center[3] = { (p1 + p2) / 2, (p2 + p3) / 2, (p3 + p1) / 2 }; to get the edge center of each edge, nothing weird there.
      But this is used later on with:
      vec3d d = center + edge_center[i]; edge_test[i] = d.len() > ratio_size; edge_test is then used to evaluate if there should be a triangle drawn or if it should be split up into 3 new triangles instead. Why is it working for him? shouldn't it be like center - edge_center or something like that? Why adding them togheter? I asume here that the center is the center of details for the LOD. the position of the camera if stood on the ground of the planet and not up int he air like it is now.

      Full code can be seen here:
      https://github.com/sp4cerat/Planet-LOD/blob/master/src.simple/Main.cpp
      If anyone would like to take a look and try to help me understand this code I would love this person. I'm running out of ideas on how to solve this in my own head, most likely twisted it one time to many up in my head
      Thanks in advance
      Toastmastern
       
       
    • 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));  
  • Popular Now