Planet atmospheres, ray-sphere intersections. 

Thanks! I love Sebastian's videos. Full of great info.

@@MartinDonald not sure if it would be in your interest, but i am currently struggling with cone/cylinder intersections for my ray tracer, so if you ever get ideas for videos about rays and intersections i have your bell turned on ;-)

Thank you very much! Really appreciated :)

I implemented this and had an odd issue. When looking directly down toward the planet there's a completely unshaded square front and centre between the camera and the planet. When looking side on I've got a nice atmo so I'm not far from the answer hopefully. I've literally just copied the shader so far and haven't gone through it properly yet but I was wondering if you have any ideas where I'm going wrong? EDIT: missed your reply, oh you're very welcome! I'm grateful to you for doing this, it's exactly what I needed explained in beautiful detail.

@@MartinDonald This is bizarre. I thought it might be the camera as mine has gimbals and zooms and all sorts so I added a new vanilla one and made that current. Same bug. Thought it might be my implementation of the shader (I'm instancing the meshes procedurally in code including the CubeMesh), so I did it that way on a fresh scene and that worked perfectly, no weird box, just not on my actual project... So it's not the shader code and it's not the camera. Grr. It's the same whether you're above the atmo or below, so it's not the neg culling. It's just like there's a "so not shade here" plane a metre from the camera... What else could it possibly be?

@@davidmurphy563 hmm sorry, I'm not sure what the problem could be, if you're rendering to a mesh cube as I do in the video then perhaps your sphere radius is too large and it's clipping with the cube? Since you're a patron you can also download my project files for this video and see if there are any clues in there 🔍

@@MartinDonald Yeah, I'm baffled by it too. Like I say, I got it going perfectly on another quick mockup project, just not my game... My radius is 10k but the CubeMesh is bigger and anyway, it's the opposite of that: the unshaded diamond shaped region is on the local -y axis between the camera and the world. Just like if there were an unshading plane as a child of the camera positioned on a tangent in the direction of the world removing the shade. There isn't such a plane obvs, that's just how it looks. Very frustrating. Anyway, sorry to pester, I'll keep plugging away. I'll try deleting the shader and making a new one, see if that fixes it.

100%

Thanks! You're absolutely right, you just need to multiply it by your cam matrix like so: vec4(light_dir.xyz, 1.0) * CAMERA_MATRIX;

@@MartinDonald works wonderfully! thanks a lot!

This is probably due to the depth buffer becoming less accurate at really long distances. You can try offsetting the depth test in the shader when the planet is really far away? Or maybe you could look into swapping your planet for a simple sprite for seriously long distances.

I suggest increasing the camera near plane when you are far away.

I had the same issue when i tried to render the atmosphere with a sphere, you need to use a cube like he said

Not a dumb question at all! 3D transforms are a nightmare. Check out this page in the godot docs, particularly the part about quaternion rotations at the end: docs.godotengine.org/en/stable/tutorials/3d/using_transforms.html

that worked for me: struct v2f { float2 uv : TEXCOORD0; float3 view : TEXCOORD1; float4 vertex : SV_POSITION; }; v2f vert (appdata v) { v2f o; o.vertex = UnityObjectToClipPos(v.vertex); o.uv = v.uv; o.view = mul(unity_ObjectToWorld, v.vertex); return o; } in fragment shader: float3 VIEW= normalize(i.view - _WorldSpaceCameraPos);

@@syuta9317 thank you

I probably can't, but I can recommend Sebastian Lague's video on planet atmospheres, which is done in Unity: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-DxfEbulyFcY.html

@@MartinDonald thank you! I have seen it but he doesn't really go in too much depth, as far as i know he only mentions the rsi, but thank you for this video. Im really close to getting it in unity hdrp, just having issues with sampling the depth texture. For some reason the screen position does not get interpolated so only the bottom left corner gets all the depth of the entire depth map. Please do keep on keeping on, im loving your videos. I understood this the first time you explained it.