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Use decomposeProjection + cleanups 
We recently added Matrix4x4.decomposeProjection, which gives us the frustum planes for the projection matrix.  I can then offset those with the jitter value, and create the jittered projection matrix.

Also a couple cleanups from PR feedback
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@robbiesri
robbiesri committed Sep 8, 2017
1 parent f9d3e71 commit 51877f6
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Showing 3 changed files with 20 additions and 71 deletions.
17 changes: 9 additions & 8 deletions PostProcessing/Runtime/Effects/TemporalAntialiasing.cs
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Expand Up @@ -136,6 +136,13 @@ public void ConfiguredStereoJitteredProjectionMatrices(PostProcessRenderContext
camera.useJitteredProjectionMatrixForTransparentRendering = false;
}

private void GenerateHistoryName(RenderTexture rt, int id, PostProcessRenderContext context)
{
rt.name = "Temporal Anti-aliasing History id #" + id.ToString();
if (XR.XRSettings.isDeviceActive)
rt.name += " for eye " + context.xrActiveEye.ToString();
}

RenderTexture CheckHistory(int id, PostProcessRenderContext context)
{
var rt = m_HistoryTextures[context.xrActiveEye][id];
Expand All @@ -145,10 +152,7 @@ RenderTexture CheckHistory(int id, PostProcessRenderContext context)
RenderTexture.ReleaseTemporary(rt);

rt = RenderTexture.GetTemporary(context.width, context.height, 0, context.sourceFormat);
if (XR.XRSettings.isDeviceActive)
rt.name = "Temporal Anti-aliasing History id #" + id.ToString() + " for eye " + context.xrActiveEye.ToString();
else
rt.name = "Temporal Anti-aliasing History id #" + id.ToString();
GenerateHistoryName(rt, id, context);

rt.filterMode = FilterMode.Bilinear;
m_HistoryTextures[context.xrActiveEye][id] = rt;
Expand All @@ -160,10 +164,7 @@ RenderTexture CheckHistory(int id, PostProcessRenderContext context)
// On size change, simply copy the old history to the new one. This looks better
// than completely discarding the history and seeing a few aliased frames.
var rt2 = RenderTexture.GetTemporary(context.width, context.height, 0, context.sourceFormat);
if (XR.XRSettings.isDeviceActive)
rt2.name = "Temporal Anti-aliasing History id #" + id.ToString() + " for eye " + context.xrActiveEye.ToString();
else
rt2.name = "Temporal Anti-aliasing History id #" + id.ToString();
GenerateHistoryName(rt2, id, context);

rt2.filterMode = FilterMode.Bilinear;
m_HistoryTextures[context.xrActiveEye][id] = rt2;
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5 changes: 1 addition & 4 deletions PostProcessing/Runtime/PostProcessRenderContext.cs
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Expand Up @@ -30,10 +30,7 @@ public Camera camera
if (camera.stereoActiveEye == Camera.MonoOrStereoscopicEye.Right)
m_xrActiveEye = (int)Camera.StereoscopicEye.Right;

if (m_xrSinglePass && (xrDesc.dimension != TextureDimension.Tex2DArray))
m_xrSingleEyeWidth = m_width / 2;
else
m_xrSingleEyeWidth = m_width;
m_xrSingleEyeWidth = XR.XRSettings.eyeTextureWidth;
}
else
{
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69 changes: 10 additions & 59 deletions PostProcessing/Runtime/Utils/RuntimeUtilities.cs
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Expand Up @@ -386,71 +386,22 @@ public static Matrix4x4 GetJitteredOrthographicProjectionMatrix(Camera camera, V
return Matrix4x4.Ortho(left, right, bottom, top, camera.nearClipPlane, camera.farClipPlane);
}

// We can represent a projection matrix by using the tangents of the frustum half angles.
// The 'traditional' representation of the values in a projection matrix for
// left, right, top and bottom are that they represent values on the near clip plane.
// If we take the matrix element (0,0) as an example, it would be equal to
// (2 * clipNearPlane) / (right - left). We can divide the term by clipNearPlane to get
// 2 / ((right - left) / clipNearPlane), which gives us
// 2 / (right/clipNearPlane - left/clipNearPlane). And we can substitue
// tan(rightHalfAngle) = (right/clipNearPlane) and tan(leftHalfAngle) = (left/clipNearPlane).
// Our new term for (0,0) is 2/(rTan - lTan).
//
// Since we have the calculated value for (0,0), we can use that to solve for (rTan - lTan).
// (rTan - lTan) = 2 / proj(0,0)
// We can also get the value for (rTan + lTan), as it is the numerator for term (0,2).
// We have the denominator, so (rTan + lTan) = (rTan - lTan) * proj(0,2) = 2 * proj(0,2) / proj (0,0)
// We can add (rTan + lTan) and (rTan - lTan) to get 2 * rTan, which can gives us rTan.
// rTan = ((2 / proj(0,0)) + (2 * proj(0,2) / proj(0,0))) / 2 =>
// rTan = (1 + proj(0,2)) / proj(0,0)
//
// We can derive lTan via proj(0,0) = 2 / (rTan - lTan), which gives us
// lTan = rTan - 2/proj(0,0)
// If we substitute our derivation for rTan in here, we get the conveniently symmetric:
// lTan = ((1 + proj(0,2)) / proj(0,0)) - 2 / proj(0,0) =>
// lTan = (-1 + proj(0,2)) / proj(0,0)
//
// We can repeat these calculations for the top and bottom tangents as well.
public static Matrix4x4 GenerateJitteredProjectionMatrixFromOriginal(PostProcessRenderContext context, Matrix4x4 origProj, Vector2 jitter)
{
var rTan = (1.0f + origProj[0, 2]) / origProj[0, 0];
var lTan = (-1.0f + origProj[0, 2]) / origProj[0, 0];
FrustumPlanes planes = origProj.decomposeProjection;

var tTan = (1.0f + origProj[1, 2]) / origProj[1, 1];
var bTan = (-1.0f + origProj[1, 2]) / origProj[1, 1];
float vertFov = Math.Abs(planes.top) + Math.Abs(planes.bottom);
float horizFov = Math.Abs(planes.left) + Math.Abs(planes.right);

float tanVertFov = Math.Abs(tTan) + Math.Abs(bTan);
float tanHorizFov = Math.Abs(lTan) + Math.Abs(rTan);
var planeJitter = new Vector2(jitter.x * horizFov / context.singleEyeWidth,
jitter.y * vertFov / context.height);

jitter.x *= tanHorizFov / context.singleEyeWidth;
jitter.y *= tanVertFov / context.height;
planes.left += planeJitter.x;
planes.right += planeJitter.x;
planes.top += planeJitter.y;
planes.bottom += planeJitter.y;

float left = jitter.x + lTan;
float right = jitter.x + rTan;
float top = jitter.y + tTan;
float bottom = jitter.y + bTan;

var jitteredMatrix = new Matrix4x4();

jitteredMatrix[0, 0] = 2f / (right - left);
jitteredMatrix[0, 1] = 0f;
jitteredMatrix[0, 2] = (right + left) / (right - left);
jitteredMatrix[0, 3] = 0f;

jitteredMatrix[1, 0] = 0f;
jitteredMatrix[1, 1] = 2f / (top - bottom);
jitteredMatrix[1, 2] = (top + bottom) / (top - bottom);
jitteredMatrix[1, 3] = 0f;

jitteredMatrix[2, 0] = 0f;
jitteredMatrix[2, 1] = 0f;
jitteredMatrix[2, 2] = origProj[2, 2];
jitteredMatrix[2, 3] = origProj[2, 3];

jitteredMatrix[3, 0] = 0f;
jitteredMatrix[3, 1] = 0f;
jitteredMatrix[3, 2] = -1f;
jitteredMatrix[3, 3] = 0f;
var jitteredMatrix = Matrix4x4.Frustum(planes);

return jitteredMatrix;
}
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