Textures in Leadwerks Engine 3
Entry posted by Josh ·
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Textures in LE3 give you more control. You can retrieve all or part of any mipmap of a texture to system memory, edit the texture, then send it back to the GPU. Fortunately, the engine checks the bounds of the texture so you don't have to worry about producing any blue screens of death, as can happen when you're having too much fun with GPU memory.
Here's some simple code to retrieve the texture from video memory into a system memory bank, modify it, and send it back to the graphics card:
Bank* pixels = new Bank( texture->GetMipmapSize(0) ); texture->GetPixels( pixels ); pixels->PokeByte( (x*height + y)*4, 255 ); texture->SetPixels( pixmap );
There are overloaded functions for raw memory pointers, but the bank syntax has a little extra error checking, since this kind of thing can easily produce BSODs.
If you want to get really fancy, there are additional parameters that will let your retrieve or send part of a texture to and from the GPU. This is something I use extensively in the terrain editing routines, which take place on the GPU (that's why terrain editing is so fast). I use a shader to modify part of the terrain heightmap, and then I have to retrieve the modified heightmap back to system memory. Because the textures can be pretty big, it's more efficient to retrieve a sub-rectangle of pixels instead of the whole texture.
I ran into some trouble with DDS compression, as the image below demonstrates. This is what happens when you accidentally offset DDS mipmap data by four bytes. (This has been fixed):
The texture loader can handle background texture loading, so if you want you can have those cool blurry textures when a level starts, and they get sharper after a few seconds. This cuts the texture load time down to practically zero. If you have a large scene with lots of large textures, this will be nice to cut level load times down.
All media files in LE3 can be reloaded with a Reload() class function. This is necessary for some of the art pipeline features in the editor, so it's being built in from the very beginning. It is pretty cool to tap a key and watch your textures reload one mipmap at a time. This also means you can change the texture quality setting on the fly and not worry about reloading textures manually...when you change the texture quality setting the engine will automatically reload all textures that came from a file.
As we saw last week, here is the proper way to load a texture and apply it to a material in LE3:
Texture* tex = LoadTexture("brickwall01.dds");
mat->SetTexture(tex);
delete tex;
It occurred to me this can be simplified with an alternate overloaded function:
mat->SetTexture("brickwall01.dds");
The same can be done with shaders. If it succeeds, true is returned, otherwise false is returned:
mat->SetShader("Shaders/simple.shader");
So that's a nice convenient feature.
It was pointed out that my Copy(int unique) syntax was confusing, and I agree, because I couldn't even remember which was which. Therefore you will have an Instance() and Copy() function for textures, shaders, entities, materials, etc. The Instance() function will act like LE2's CopyEntity(), and the Copy() function will make a unique copy that can be modified without altering the original.
Texture animation is supported, out of the box. I'm using the old Quake naming convention where you add +framenumber to the end of the texture to specify an animation. For example, if you load "fire+01.dds", the engine will look for "fire+02.dds", "fire+03.dds", etc., until all frames are loaded. The texture will automatically switch frames with an animation speed you specify. It should be possible to convert AVI files into a sequence of separate frames, but I haven't looked into it yet.
That's all I have for now. It feels like I am really in the thick of LE3 development now. I've already done most of the graphics stuff with LE2, so I know how to do that. What I am really looking forward to is the high-level features, particularly the script and flowgraph implementation. I like to attack unknowns first, because the more I know, the better I can design the engine. We already know we can do fantastic graphics, and I understand how that all works. It would make sense to focus on areas that I haven't developed as extensively in the past...networking, gameplay, and the art pipeline. Therefore, we may see a Leadwerks 3 beta with just basic graphics and a focus on gameplay features first.
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