[BlackBerry] Improved unproject algorithm

• Component: WebKit BlackBerry
• Status: RESOLVED INVALID

[Arvid Nilsson]

Instead of doing perspective-correct texturing to unproject, map from
view (x,y) coordinates to view (x,y,z) coordinates by finding the
corresponding z coordinate in the plane of the layer. Then map from view coordinates to (normalized) model coordinates using the inverse model-view matrix.

Now this gets slightly awkward because the unproject method accepts
normalized device coordinates as input, so we have to move to view
space. In the future, we should update the code to mainly work with
view coordinates and only transform to normalized device coordinates at
the very end (e.g. in the shader).

For now though, this means we need to store yet another matrix (which
will hopefully make m_drawTransform obsolete eventually) and we need
to invert what we can of the (orthographic) projection matrix.

However, it's all worth it because the new unprojection code is much
faster and more numerically stable. And the w's aren't needed any more.

[Arvid Nilsson]

Created attachment 210112 [details]
Patch

[Jacky Jiang]

Comment on attachment 210112 [details]
Patch

Looks good to me, r+ internally.

[Rob Buis]

Comment on attachment 210112 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=210112&action=review

Looks good.

> Source/WebCore/ChangeLog:7
> +        Internally reviewed by NOBODY (OOPS!).

This  line will probably not work, at least not with cq+, it should work when pushing by hand.

[Arvid Nilsson]

Comment on attachment 210112 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=210112&action=review

> Source/WebCore/platform/graphics/blackberry/LayerCompositingThread.cpp:135
> +    m_modelViewTransform = projectionMatrix;

Oops, I recreated this patch from memory for the review, but got this bit wrong - it's the model-view bit we want, not the projection bit! Should be

    m_modelViewTransform = matrix;

> Source/WebCore/platform/graphics/blackberry/LayerUtilities.h:251
> +    AffineTransform inverseProjectionMatrix(projectionMatrix.m11(), projectionMatrix.m21(), projectionMatrix.m21(), projectionMatrix.m22(), projectionMatrix.m41(), projectionMatrix.m42());

Typo, I wrote m21 twice... Should be AffineTransform inverseProjectionMatrix(projectionMatrix.m11(), projectionMatrix.m21(), projectionMatrix.m12(), projectionMatrix.m22(), projectionMatrix.m41(), projectionMatrix.m42());

[Arvid Nilsson]

Created attachment 210266 [details]
Patch

[Arvid Nilsson]

(In reply to comment #5)
> Created an attachment (id=210266) [details]
> Patch

Fixed typos, sorry about those

[Arvid Nilsson]

This is a followup to 120362