I am trying to create a card game. I want to have a deck of cards where the back of the card is a fixed texture but the front is dynamic, i.e. it has some text fields on it as well as a picture. I have created a box sized 3x2x0.16 to represent my card. I can get the fixed texture to load but I cannot find any code examples on the web that show me how to load a fixed texture on one side of the box and a dynamic one on the other. Can anyone point me to some examples please. I'm using DirectXTK mainly, but can probably fathom it out from any DirectX code too.
DirectX11 is version of DirectX I am using.
Any recommendations on how to do this would also be welcome.
Thanks
Easiest method for generating your cards, depending on how many there are and how large you want them, is to generate the faces at startup by using render to texture. Effectively, draw your dynamic card faces exactly like you would draw them in the world, but use an orthographic projection matrix and a blank 2D texture object as the render target. Once you have that, cache these "dynamic" textures in an std::map and bind them when drawing a specific card.
If your faces are relatively small, or you want to save on texture memory, you can stitch multiple card faces together into a large sheet of textures, then use some shader scaling logic to reference a subsection of the sheet for rendering a specific texture. With this, you can assemble "decks" of cards that only contain the faces in use in that particular game, allowing you to evict the others from GPU RAM.
Related
So I have a simple OpenGL viewer where you can draw any number of boxes that the user wants. Ive also added the ability to take a PNG or JPG image and texture map it to a primitive.
I want to be able to have the user specify any of the cubes on the screen and apply different textures to them. Im fairly new to OpenGL. Right now I can easily map an image to a single primitive, but Im wondering whats the best way to map 2 seperate images (which may be different sizes) to 2 separate primitives.
Ive done a fair amount of reading up on 2D Texture arrays and it would seem this would be the way I wanna go since I can store multiple textures in one texture unit, but I'm not sure if this is possible considering what I mentioned above. If the images are both different dimensions then I dont think I can do this (at least I dont think so). I know I can just store each image into separate texture units but doing it in an array seemed like the cleaner way to do it.
What would be the best way to do this? Can you in fact store different size images into a 2d texture array? And if so how? Or am I better off just storing them on separate texture units?
Texture arrays are mainly meant if you want to draw a single primitive (or a whole mesh) with the shader being able to select between images without exhausting the number of available texture sampling units. You can use them in the way you thought, but I doubt it will benefit you. Another approach (which is similiar to texture arrays) is using a texture atlas, i.e. creating a patchwork of images that constitutes a single texture and using appropriate texture coordinates to select the subimage.
In your case, I suggest simply load each picture into a separate texture and bind the appropriate texture before drawing the cube.
Is there a way to extract a point cloud from a rendered 3D Scene (using OPENGL)?
in Detail:
The input should be a rendered 3D Scene.
The output should be e.g a three dimensional array with vertices(x,y,z).
Mission possible or impossible?
Render your scene using an orthographic view so that all of it fits on screen at once.
Use a g-buffer (search for this term or "fat pixel" or "deferred rendering") to capture
(X,Y,Z, R, G, B, A) at each sample point in the framebuffer.
Read back your framebuffer and put the (X,Y,Z,R,G,B,A) tuple at each sample point in a
linear array.
You now have a point cloud sampled from your conventional geometry using OpenGL. Apart from the readback from the GPU to the host, this will be very fast.
Going further with this:
Use depth peeling (search for this term) to generate samples on surfaces that are not
nearest to the camera.
Repeat the rendering from several viewpoints (or equivalently for several rotations
of the scene) to be sure of capturing fragments from a the nooks and crannies of the
scene and append the points generated from each pass into one big linear array.
I think you should take your input data and manually multiply it by your transformation and modelview matrices. No need to use OpenGL for that, just some vector/matrices math.
If I understand correctly, you want to deconstruct a final rendering (2D) of a 3D scene. In general, there is no capability built-in to OpenGL that does this.
There are however many papers describing approaches to analyzing a 2D image to generate a 3D representation. This is for example what the Microsoft Kinect does to some extent. Look at the papers presented at previous editions of SIGGRAPH for a starting point. Many implementations probably make use of the GPU (OpenGL, DirectX, CUDA, etc.) to do their magic, but that's about it. For example, edge-detection filters to identify the visible edges of objects and histogram functions can run on the GPU.
Depending on your application domain, you might be in for something near impossible or there might be a shortcut you can use to identify shapes and vertices.
edit
I think you might have a misunderstanding of how OpenGL rendering works. The application produces and sends to OpenGL the vertices of triangles forming polygons and 3d objects. OpenGL then rasterizes (i.e. converts to pixels) these objects to form a 2d rendering of the 3d scene from a particular point of view with a particular field of view. When you say you want to retrieve a "point cloud" of the vertices, it's hard to understand what you want since you are responsible for producing these vertices in the first place!
I would like to know if there is a way to generate a single static image of a 3D object (1 single object represented as a triangle list), using OpenGL or DirectX, that allows you to know which specific triangles defining the object have been used to generate every one of the pixels forming the rendered image. I've cited OpenGL and DirectX because they are widely used APIs graphics if somebody knows other ways of achieving the previous that works at high speed I would be also interested in his/her answer. I currently use my own software implementation of the rendering pipeline to keep track of the relationship, but I would like to use the power and effects (mainly antialiasing, shadows and specific skin rendereing techniques) that graphics cards offer.
Thanks very much for your help
Sure, just output a triangle identifier to a separate render-target (using MRT). In GLSL-terms, this is gl_PrimitiveID, and in HLSL-terms it's SV_PrimitiveID. If you are using multi-sampling, then your multi-sample buffer for that render-target become a list of primitives that contribute to each pixel.
Draw each triangle in a different colour. R8G8B8 offers you about 16.7 million possible colours, so one can index that number of triangles with it. You don't have to draw to a on-screen buffer. You could render the picture as usual, and render to a second target, indexing the triangles in a off-screen buffer.
Is it a good or bad idea to use display lists for drawing textured rectangles?
The display list would be re-compiled only if the texture the sprite is using changes.
For drawing a single sprite, there's no real problem in doing it that way, but there's no advantage to it either, assuming you're using glRotate/glTranslate to position the sprite. Plenty of games have been written that way.
In my games, I use a vertex buffer object with GL_DYNAMIC_DRAW to store all the sprites which share each texture atlas. I update the vert positions on the CPU and send the whole batch in one draw call. I can draw many more sprites using this approach. I could do the positions in a vertex shader if I needed to draw even more.
Also, keep in mind that OpenGL ES2 doesn't support display lists, so if you're thinking of porting to an ES2 device you'd have to re-do it. (iPhone/iPad support ES1 but you can't mix and match with ES2, you can use display lists OR shaders but not both).
I'm creating a tile-based game in C# with OpenGL and I'm trying to optimize my code as best as possible.
I've read several articles and sections in books and all come to the same conclusion (as you may know) that use of VBOs greatly increases performance.
I'm not quite sure, however, how they work exactly.
My game will have tiles on the screen, some will change and some will stay the same. To use a VBO for this, I would need to add the coordinates of each tile to an array, correct?
Also, to texture these tiles, I would have to create a separate VBO for this?
I'm not quite sure what the code would look like for tiling these coordinates if I've got tiles that are animated and tiles that will be static on the screen.
Could anyone give me a quick rundown of this?
I plan on using a texture atlas of all of my tiles. I'm not sure where to begin to use this atlas for the textured tiles.
Would I need to compute the coordinates of the tile in the atlas to be applied? Is there any way I could simply use the coordinates of the atlas to apply a texture?
If anyone could clear up these questions it would be greatly appreciated. I could even possibly reimburse someone for their time & help if wanted.
Thanks,
Greg
OK, so let's split this into parts. You didn't specify which version of OpenGL you want to use - I'll assume GL 3.3.
VBO
Vertex buffer objects, when considered as an alternative to client vertex arrays, mostly save the GPU bandwidth. A tile map is not really a lot of geometry. However, in recent GL versions the vertex buffer objects are the only way of specifying the vertices (which makes a lot of sense), so we cannot really talked about "increasing performance" here. If you mean "compared to deprecated vertex specification methods like immediate mode or client-side arrays", then yes, you'll get a performance boost, but you'd probably only feel it with 10k+ vertices per frame, I suppose.
Texture atlases
The texture atlases are indeed a nice feature to save on texture switching. However, on GL3 (and DX10)-enabled GPUs you can save yourself a LOT of trouble characteristic to this technique, because a more modern and convenient approach is available. Check the GL reference docs for TEXTURE_2D_ARRAY - you'll like it. If GL3 cards are your target, forget texture atlases. If not, have a google which older cards support texture arrays as an extension, I'm not familiar with the details.
Rendering
So how to draw a tile map efficiently? Let's focus on the data. There are lots of tiles and each tile has the following infromation:
grid position (x,y)
material (let's call it "material" not "texture" because as you said the image might be animated and change in time; the "material" would then be interpreted as "one texture or set of textures which change in time" or anything you want).
That should be all the "per-tile" data you'd need to send to the GPU. You want to render each tile as a quad or triangle strip, so you have two alternatives:
send 4 vertices (x,y),(x+w,y),(x+w,y+h),(x,y+h) instead of (x,y) per tile,
use a geometry shader to calculate the 4 points along with texture coords for every 1 point sent.
Pick your favourite. Also note that directly corresponds to what your VBO is going to contain - the latter solution would make it 4x smaller.
For the material, you can pass it as a symbolic integer, and in your fragment shader - basing on current time (passed as an uniform variable) and the material ID for a given tile - you can decide on the texture ID from the texture array to use. In this way you can make a simple texture animation.