![]() ![]() So first we need to figure out which direction is forward for the camera. This is all relative to the camera's coordinate space. Same for Y but obviously in the Y direction. We assume the center shoots straight forward, the very left will shoot to the left of the view box and the right will shoot toward the right of the view box. Using the pixel ratio about we can figure out the x and y the ray is pointing toward. The image data is a flat array of pixels represented by 4 bytes for RGBA, so we need to add an extra *4 to move from pixel to pixel. If you've never done direct pixel manipulation on a canvas, you need to getImageData and then iterate across the rows and columns. Finally we divide that by half the pixel width to get how much a coordinate changes per pixel. Anyway, we can get the aspect ratio of the canvas and multiply the half width (also 1 unit) by it to get a correct aspect ratio image (if you chose 1 and the canvas wasn't square you'll get squished images). I'm just going to assume you're using a monitor since web development on a phone is hard. Depending on the dimensions of the rendering surface you might need something wider than tall (typically on monitors but if this were for phones you might want to flip it). ![]() The half height is 1 because the view port's top is at and the center is at so 1 unit of Y spans half the screen. As it turns out finding the half-width and half-height values are more useful because we can use them elsewhere. ![]() Once the space is defined we can find the amount of change in view coordinate per amount in change in pixels. If you wanted a different base scale you can change those. Typically the left edge is, right is, top is, bottom is with the center at so we'll just pick that. We actually did this in WebGL when we defined "clip space". So what direction do we shoot the rays? There's a few way to do this but a simple perspective correct way is to visualize the view window as a box in space. For this most simple version, we'll just test if anything was hit and draw that pixel in red. The way it works is that we will start from the top row and go column by column, row by row casting a ray out. One of the nice things to modeling pixels this way is that we don't need to directly worry about perspective transforms. Rays are shot from the center of the camera in different directions. If you followed along with the previous series these are the same, I've just removed some functions we aren't using to simplify. Let's start with a base:Įxport class WcGeoRt extends HTMLElement Įnter fullscreen mode Exit fullscreen mode Please reference that series: Īs will my other projects we'll contain the whole engine inside a web component. This is my attempt (though I don't expect expect it to get to "real-time" performance).Īlso, we'll borrow code from the WebGL engine because many parts are still the same. ![]() Despite that we can still make ray tracing engines that have real-time performance, even if they need to sacrifice resolution and frame-rate. Each pixel on the screen is a ray that can have technically infinite bounces. Its simply not used as much because it's very expensive. One of the nice thing about raytracing is that it is much more accurate at simulating light but on top of that it's actually much simpler than some of the concepts going on in raster graphics using WebGL. Ray tracing has gotten a bit of a promotional bump due to the hardware raytracing units built into modern GPUs. As my WebGL 3D engine gets more mature I thought it would be a good idea to dip a little into raytracing. ![]()
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