Camera raycast error

hi,

The following code is supposed to cast a ray from camera to almost each pixel in camera's view, but the result is wrong. Why ?

Code (CSharp):

1. using System;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEditor;
5.  
6. [CustomEditor(typeof(Camera))]
7. public class CameraEditor:Editor
8. {
9.     private void OnSceneGUI()
10.     {
11.         if (Event.current.type != EventType.Repaint)
12.             return;
13.  
14.         Camera camera = target as Camera;
15.         Transform t = camera.transform;
16.         float h = Mathf.Tan(camera.fieldOfView);
17.         float w = h * camera.aspect;
18.  
19.         Vector3
20.             forward = t.forward,
21.             right = t.right,
22.             up = t.up,
23.             dir, cameraPos = t.position;
24.         Debug.Log(h + ":" + w);
25.  
26.         int count = (camera.scaledPixelWidth * camera.pixelHeight);
27.  
28.         Handles.Label(cameraPos, "Pixel Count : " + count + " w:" + camera.pixelWidth + " h:" + camera.pixelHeight);
29.         float x, y;
30.         for(int i = 0; i < count; i+=1000)
31.         {
32.             x = i % camera.pixelWidth - camera.pixelWidth * 0.5f;
33.             y = i / camera.pixelHeight - camera.pixelHeight * 0.5f;
34.  
35.             dir = (forward + x * w * right + y * h * up).normalized;
36.  
37.             Handles.color = new Color(dir.x, dir.y, dir.z, 1);
38.             //Handles.Label(cameraPos + dir, x + ":" + y + ":" + dir);
39.             Handles.DrawLine(cameraPos, cameraPos + dir);
40.         }
41.     }
42. }
43.  

Result :



Thanks

 

Line 33 your modulo should be with the width, not with height.

When one iterates all the pixels on a raster screen from 0 to w*h-1, one derives cartesian coordinates with:

Code (csharp):

1. int x = i % w;
2. int y = i / w;

You don't use h for that purpose, assuming you're going across scanline wise, then down one line, etc.

PS: note that your for loop is also stepping by +1000 right now, but I assume that is for rapid testing purposes...

 

Yes, i++ draw millions handles lines and kill the fps.
I found another solution but yours is shorter. Thanks.

I tried to port this to my post process shader but it still buggy. It is supposed to draw pixel ray or white if pointing at a sphere at world center with a radius of 2. But it only draw the ray as a color or full white if the camera is inside the sphere. It's a raymarching with signed distance function.

Code (CSharp):

1. Shader "Hidden/Custom/RayMarcher"
2. {
3.     HLSLINCLUDE
4. #include "Packages/com.unity.postprocessing/PostProcessing/Shaders/StdLib.hlsl"
5. #include "DistanceFunctions.cginc"
6.  
7.     uniform float3
8.         forward,
9.         right,
10.         up;
11.  
12.     uniform float _maxDistance;
13.     uniform float fov;
14.     uniform float aspect;
15.  
16.     struct VertexInput
17.     {
18.         float4 vertex : POSITION;
19.     };
20.  
21.     struct v2f
22.     {
23.         float4 vertex : SV_POSITION;
24.         float4 ray : TEXCOORD0;
25.     };
26.  
27.     inline float4 ComputeNonStereoScreenPos(float4 pos) {
28.         float4 o = pos * 0.5f;
29.         o.xy = float2(o.x, o.y * _ProjectionParams.x) + o.w;
30.         o.zw = pos.zw;
31.         return o;
32.     }
33.  
34.     inline float4 ComputeScreenPos(float4 pos) {
35.         float4 o = ComputeNonStereoScreenPos(pos);
36. #if defined(UNITY_SINGLE_PASS_STEREO)
37.         o.xy = TransformStereoScreenSpaceTex(o.xy, pos.w);
38. #endif
39.         return o;
40.     }
41.  
42.     v2f vert(VertexInput v)
43.     {
44.         v2f o;
45.  
46.         o.vertex = float4(v.vertex.xyz, 1.0);
47.  
48.         float4 screenpos = ComputeScreenPos(v.vertex);
49.         o.ray = screenpos;
50.  
51.         return o;
52.     }
53.  
54.     float distanceField(float3 p) {
55.         return sdSphere(p - float3(0, 0, 0), 2.0);
56.     }
57.  
58.     float4 raymarching(float3 ro, float3 rd, float depth)
59.     {
60.         float4 result = float4(0, 0, 0, 1);
61.  
62.         const int maxi = 64;
63.         float t = 0;
64.         float d;
65.         float3 p;
66.         for (int i = 0; i < maxi; i++)
67.         {
68.             if (t > _maxDistance)
69.             {
70.                 result = float4(rd, 1);
71.                 break;
72.             }
73.  
74.             p = ro + rd * t;
75.             d = distanceField(p);
76.             if (d < 0.01) {
77.                 result = float4(1, 1, 1, 1);
78.                 break;
79.             }
80.  
81.             t += d;
82.         }
83.  
84.         return result;
85.     }
86.  
87.     static float h = tan(fov);
88.     static float w = h * aspect;
89.  
90.     float4 frag(v2f i) : SV_Target
91.     {
92.         float3 rayOrigin = _WorldSpaceCameraPos;
93.  
94.         float x = i.ray.x * 2.0f - 1.0f;
95.         float y = i.ray.y * 2.0f - 1.0f;
96.  
97.         float3 dir = normalize(forward + x * w * right + y * h * up);
98.  
99.         float4 result = raymarching(rayOrigin, dir, 1000);
100.         return result;
101.     }
102.     ENDHLSL
103.  
104.     SubShader
105.     {
106.         // No culling or depth
107.         Cull Off
108.         ZWrite Off
109.         ZTest Always
110.  
111.         Pass
112.         {
113.             HLSLPROGRAM
114.             #pragma vertex vert
115.             #pragma fragment frag
116.             #pragma target 3.0
117.             ENDHLSL
118.         }
119.     }
120. }

The raymarcher c# class :

Code (CSharp):

1. using System;
2. using System.Collections;
3. using System.Collections.Generic;
4. using UnityEngine;
5.  
6. using UnityEngine.Rendering.PostProcessing;
7.  
8. [Serializable][ExecuteAlways]
9. [PostProcess(typeof(RayMarcherRenderer), PostProcessEvent.AfterStack, "Custom/RayMarcher", true)]
10. public class RayMarcher : PostProcessEffectSettings
11. {
12.     public float _maxDistance;
13.  
14.     public FloatParameter MaxDistance = new FloatParameter { value = 100.0f };
15. }
16.  
17. [ExecuteAlways]
18. public sealed class RayMarcherRenderer : PostProcessEffectRenderer<RayMarcher>
19. {
20.     public override void Render(PostProcessRenderContext context)
21.     {
22.         PropertySheet sheet = context.propertySheets.Get("Hidden/Custom/RayMarcher");
23.  
24.         Camera camera = context.camera;
25.  
26.         sheet.properties.SetVector("forward", camera.transform.forward);
27.         sheet.properties.SetVector("right", camera.transform.right);
28.         sheet.properties.SetVector("up", camera.transform.up);
29.         sheet.properties.SetFloat("fov", camera.fieldOfView * Mathf.Deg2Rad * 0.5f);
30.         sheet.properties.SetFloat("aspect", camera.aspect);
31.         sheet.properties.SetFloat("_MaxDistance", settings.MaxDistance);
32.         context.command.BlitFullscreenTriangle(context.source, context.destination, sheet, 0);
33.     }
34. }
35.  

And the result looks ok for the rays, but the sphere is nowhere :

 

I screwed up with _maxDistance _MaxDistance and MaxDistance...