Planar reflection clipping problem

Graphics
#1

Hello. Can someone tell me the possible cause of the problem seen in the video and how I can get rid of it?

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#2

Looks like your not setting the camera clip plane to cut at the water level , this would give you artifacts like this.

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#3

Thank you. I tried to do this by reviewing the article here, but I was unsuccessful.

I used to use DX9 based Acknex engine. I am unfamiliar with DX11. I was using a method like below to overcome this issue in Acknex:

//RENDER EVENT
function render_event()
{
	terrain_material.skill1 = floatv(render_view.portal_z);
	terrain_material.skill2 = floatv(render_view.pnormal_z);

	//if the material is rendered by the reflection camera
	if(render_view==view_reflection)
	{
		terrain_material.skill3 = 1;
	}
	else
	{	
		terrain_material.skill3 = 0;
	}
}
MATERIAL* terrain_material =
{

	flags=ENABLE_TREE ;
	event=render_event;
	effect="terrain.fx";
}


//////////////////////////////
// HLSL terrain.fx
//////////////////////////////
//vertex shader
float4 PosWorld = mul(inPos, matWorld); 

//if the material is rendered by the reflection camera
if(skill3 == 1.0)
{
	Out.Tex1.z = (PosWorld.y-skill1)*skill2;
	//Out.Tex1.z=(WorldPosition-render_view.portal_z)*render_view.pnormal_z;
}

//pixel shader
clip(In.Tex1.z);

In the example: When the terrain was rendered by the reflection camera, the plane was clipped with the clip function in the hlsl of the terrain.

In Flax, on the other hand, I don’t know how to check if a material is rendered by a specific camera. Is there a way to do this? Or maybe this method is useless for DX11? Do I need to use a completely different method?

I’ve tried a lot of things since yesterday, but I guess the real problem is that I don’t know what method to follow. I would be glad if someone could guide me.

#4

Well I think I’ve made some progress.

clip
clip1310×1836 246 KB

Now all I need is to be able to check if the object is rendered by a specific (planar) camera and clip it only when rendering by that.

As far as i understand, Unity has the OnWillRenderObject() function for that. Is there a similar function in Flax?

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#5

There is no OnWillRenderObject equivalent and culling data is internal to renderer.

#6

So there is no solution to this problem?

#7

You could manually perform Frustum Culling fro the planar camera viewpoint (Camera.Frustum).

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#8

I think achieving that is beyond my abilities. I don’t even know how to adapt the Unity codes I found to Flax. CalculateObliqueMatrix etc… Thanks anyway.

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#9

Hello again. I found an example on the Flax Discord channel and at this link. It’s supposed to clip everything below the water. I am trying to use it with OnPreRender but no success. Can anyone tell me what’s wrong/missing with this code:

using System;
using FlaxEngine;

namespace Game
{
	public class Planar : Script
	{
			
		public override void OnEnable()
		{
			..............
			_task.PreRender += OnPreRender;
			...............	
		}
		private static float sgn(float a)
		{
			if (a > 0.0f) return 1.0f;
			if (a < 0.0f) return -1.0f;
			return 0.0f;
		}

		static Vector4 CameraSpacePlane(Camera cam, Vector3 pos, Vector3 normal, float sideSign)
		{
			var renderView = new RenderView();
			renderView.CopyFrom(cam);

			Vector3 offsetPos = pos + normal * 0.07f;
			Matrix m = renderView.View;

			Vector3 point = MultiplyPoint(m,new Vector3(0.0f, 0.0f, 0.0f)).Negative; //(inverse?)
			Vector3 cpos = MultiplyPoint(m, offsetPos);
			cpos -= new Vector3(0.0f, point.Y, 0.0f);

			Vector3 cnormal = MultiplyVector(m, normal).Normalized * sideSign;
			return new Vector4(cnormal.X, cnormal.Y, cnormal.Z, -Vector3.Dot(cpos, cnormal));
		}
		public static Vector3 MultiplyPoint(Matrix matr, Vector3 point)
		{
			Vector3 res;
			float w;
			res.X = matr.M11 * point.X + matr.M12 * point.Y + matr.M13 * point.Z + matr.M14;
			res.Y = matr.M21 * point.X + matr.M22 * point.Y + matr.M23 * point.Z + matr.M24;
			res.Z = matr.M31 * point.X + matr.M32 * point.Y + matr.M33 * point.Z + matr.M34;
			w = matr.M41 * point.X + matr.M42 * point.Y + matr.M43 * point.Z + matr.M44;

			w = 1F / w;
			res.X *= w;
			res.Y *= w;
			res.Z *= w;
			return res;
		}
		public static Vector3 MultiplyVector(Matrix matr, Vector3 vector)
		{
			Vector3 res;
			res.X = matr.M11 * vector.X + matr.M12 * vector.Y + matr.M13 * vector.Z;
			res.Y = matr.M21 * vector.X + matr.M22 * vector.Y + matr.M23 * vector.Z;
			res.Z = matr.M31 * vector.X + matr.M32 * vector.Y + matr.M33 * vector.Z;
			return res;
		}

		static void CalculateObliqueMatrix(ref Matrix projection, Vector4 clipPlane)
		{
			Vector4 q = Vector4.Transform(new Vector4(
			sgn(clipPlane.X),
			sgn(clipPlane.Y),
			1.0f,
			1.0f
			), Matrix.Invert(projection));
			Vector4 c = clipPlane * (2.0f / (Vector4.Dot(clipPlane, q)));
			// third row = clip plane - fourth row
			projection[2] = c.X - projection[3];
			projection[6] = c.Y - projection[7];
			projection[10] = c.Z - projection[11];
			projection[14] = c.W - projection[15];
		}

		private void OnPreRender(GPUContext context, ref RenderContext renderContext)
		{
			Matrix view = _task.View.View;
			Matrix proj = _task.View.Projection;
			Vector4 clipPlaneCameraSpace = CameraSpacePlane(_task.Camera, Actor.Position, Actor.Transform.Up, 1.0f);
			CalculateObliqueMatrix(ref proj, clipPlaneCameraSpace);
			renderContext.View.SetUp(ref view, ref proj);
		}

	}
}
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