Reading the tutorial part 8 "Geometry" i got the impression that the following should be possible:

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Transform<double, 2, Projective> t;
Vector2d p;
Vector2d q = t * p;


But when compiling i get the following error:

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Core/Product.h(583): error C2338: INVALID_MATRIX_PRODUCT


Replacing the transform type Projective by Affine in the code, the multiplication compiles (and works) fine.

There is a workaround by homogenizing manually, but isn't that done internally?

I am using Eigen 3.0.5 with MSVC 10.

Kind regards
Janosch

right, there must be a good reason for that but I cannot remember. The solution is to explicitly use homogeneous vectors:

q = (t * p.homogeneous()).hnormalized();

gagabla wrote:There is a workaround by homogenizing manually, but isn't that done internally?

This is not done internally because in the projective case you can map any 2D point to a point at infinity. A point at infinity (or ideal point) has a homogeneous coordinate of 0 and such a point cannot be normalized.

HTH,
Hauke

on the other hand, I think that the ".homogeneous()" could be implicit just like it is the case with Affine transforms.

ggael wrote:on the other hand, I think that the ".homogeneous()" could be implicit just like it is the case with Affine transforms.

You'ld be risking Inf entries but maybe that is reasonable when the user explicitly requests the transformation of 2D points. So, I agree, we might adapt the code.

Regards,
Hauke