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I think you are getting confused between SDL_Render and SDL_GPU. SDL_Render is the old accelerated API that was only suitable for 2D games (or very primitive looking 3D ones). SDL_GPU is a fully-featured wrapper around modern 3D APIs (well, the rasteriser and compute parts anyway, no raytracing or mesh shaders there yet).

I was referencing the historical motivations that led to where we are today. Yes, I was referring in part to the SDL_Render family APIs. These were insufficient to support things like Nuklear and Dear ImGui, which are reasonable use cases for a simple 2D game, which SDL hoped to help with by introducing the SDL_Render APIs in SDL 2.0 in the first place.

https://www.patreon.com/posts/58563886

Short excerpt:

    One day, a valid argument was made that basic 2D triangles are pretty powerful in themselves for not much more code, and it notably makes wiring the excellent Dear Imgui library to an SDL app nice and clean. Even here I was ready to push back but the always-amazing Sylvain Becker showed up not just with a full implementation but also with the software rendering additions and I could fight no longer. In it went.

The next logical thing people were already clamoring for back then was shader support. Basically, if you can provide both batching (i.e. triangles) and shaders, you can cover a surprising amount of use cases, including many beyond 2D.

So fast forwarding to today, you're right. Glancing at the commit, the GPU API has 80 functions. It is full-featured beyond its original 2D roots. I haven't followed the development enough to know where they are drawing the lines now, like would raytracing and mesh shaders be on their roadmap, or would those be a bridge too far.

> where they are drawing the lines now

From what I understand, they are only going to support features that are widely supported and standardised. Thus, even bindless didn't make the cut. Raytracing, mesh shaders, work-graphs, etc. almost certainly won't make it until SDL4 10 years from now; but I am not part of the development team, so don't quote me.

Does SDL3 still use integers for coordinates? I got annoyed enough by coordinates not being floating point in SDL2 that I started learning WebGPU, instead. This was even though the game I was working on was 2D.

The issue is, if you want complete decoupling (in the sense of orthogonality) among all four of:

- screen (window) size & resolution (especially if game doesn't control)

- sprite/tile image quantization into pixels (scaling, resolution)

- sprite display position, with or without subpixel accuracy

- and physics engine that uses floating point natively (BulletPhysics)

then to achieve this with integer drawing coordinates requires carefully calculating ratios while understanding where you do and do not want to drop the fractional part. Even then you can still run into problem such as, accidentally having a gap (one pixel wide blank column) between every 10th and 11th level tile because your zoom factor has a tenth of a pixel overflow, or jaggy movement with wiggly sprites when the player is moving at a shallow diagonal at the same time as the NPC sprites are at different floating point or subpixel integer coords.

A lot of these problems could be (are) because I think of things from bottom up (even as my list above is ordered) where a physics engine, based on floating point math, is the source of Truth, and everything above each layer is just a viewport abstracting something from the layer beneath. I get the impression SDL was written by and for people with the opposite point of view, that the pixels are important and primary.

And all (most) of these have solutions in terms of pre-scaling, tracking remainders, etc. but I have also written an (unfinished) 3D engine and didn't have to do any of that because 3D graphics is floating point native. After getting the 2D engine 90% done with SDL2 (leaving 90% more to go, as we all know), I had a sort of WTF am I even doing moment looking at the pile of work-arounds for a problem that shouldn't exist.

And I say shouldn't exist because I know the final output is actually using floating point in the hardware and the driver; the SDL1/2 API is just applying this fiction that it's integers. (Neither simple, nor direct.) It gets steam coming out my ears knowing I'm being forced to do something stupid to maintain someone else's fiction, so as nice as SDL otherwise is, I ultimately decided to just bite the bullet and learn to program WebGPU directly.

>Does SDL3 still use integers for coordinates?

No, they added float versions for most functions and I think they plan on deprecating the int API in the future. The only exception I can think of offhand is still needing an integer rect to set a viewport.

That's good, then. Honestly an integer rect for the viewport is, "not wrong."

SDL2 added floating point versions of most rendering functions

I was messing around a bit with SDL2 and either I was doing something wrong or it was just plain slow. My machine is plenty fast, but even just blitting a few dozen PNGs around a screen 60 times a second was pushing its limits. I freely admit I may have been doing something wrong, but I was surprised at just how inefficient it was at a task that we used to do without too much trouble on 1Mhz CPUs.

Maybe SDL_RenderCopy is the wrong API to use to blit things from a sprite sheet onto a display? The docs didn't give any warning if this is the case.

How recent a version were you using? Plenty of games and graphical apps use SDL2 under the hood, and rendering rects from a spritesheet is trivial. Recent versions use the geometry API for rendering rects, so it should be able to handle tons of sprites without much effort.

I'm using SDL2 2.30.0. The main loop is pretty simple, it does a few SDL_RenderFillRects to create areas, then several SDL_RenderCopy where the source is a SDL_Texture created from a SDL_Surface using SDL_CreateTextureFromSurface that was loaded from files at boot. A final call to SDL_RenderPresent finishes it off. They do include an alpha channel however.

I was expecting the sprite blitting to be trivial, but it is surprisingly slow. The sprites are quite small, only a few hundred pixels total. I have a theory that it is copying the pixels over the X11 channel each time instead of loading the sprite sheets onto the server once and copying regions using XCopyArea to tell the server to do its own blitting.

This should be plenty fast. SDL_RenderCopy generally should be doing things the 'right' way for on any video card made roughly in the last 15ish years (basically binding a texture in GPU RAM to a quad).

You probably need to due some debugging/profiling to find where your problem is. Make sure you aren't creating SDL_Textures (or loading SDL_Surfaces) inside your main game play loop. You also may want to check what backend the SDL_Renderer is utilizing (e.g. OpenGL, Direct3D, Vulkan, Metal, software). If you are on software, that is likely your problem. Try forcing it to something hardware accelerated.

Also, I vaguely recall there was a legacy flag on SDL_Surfaces called "hardware" or "SDL_HWSURFACE" or "SDL_HWACCEL" or something. Don't set that. It was a a very legacy hardware from like 25 years ago that is slow on everything now.

Whatever the problem is, it probably isn't SDL. Here's a test project I worked on[0], and I'm using a garbage laptop. The sprites aren't that big but if you're just using a single texture it shouldn't matter, since SDL does sprite batching anyway.

Your theory might be right - the first thing I would look for was something allocating every frame.

You might ask the SDL Discourse forum and see what they think: https://discourse.libsdl.org/

[0]https://cdn.masto.host/krappmastohost/media_attachments/file...

> Plenty of games and graphical apps use SDL2 under the hoo

How many of them use the render API though rather than just using SDL to create a window and handle input (and perhaps manage an OpenGL context).

Is 60 FPS your screen refresh rate? Perhaps you have VSync enabled.

I see, interesting.