Backface culling in BaseDraw?

Helper

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On 08/07/2012 at 03:37, xxxxxxxx wrote:

User Information:
Cinema 4D Version:   R12/R13
Platform:
Language(s) :     C++ ;

---------
Hello people.

My ToolData plugin draws some lines into the editor. I want the lines behind the object to be hidden, but they're still rendered.

Thanks,
-Niklas

Helper

THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED

On 08/07/2012 at 06:10, xxxxxxxx wrote:

Never done this myself but if I did I'd start with BaseView::BackfaceCulling and would use that to only draw the lines for non-hidden faces.

Helper

THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED

On 08/07/2012 at 07:26, xxxxxxxx wrote:

ah, I haven't found this function! Thank you very much! It looks exactly like what I search for.

-Nik

Helper

THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED

On 09/07/2012 at 05:48, xxxxxxxx wrote:

Hi spedler,

Hm, the method doesn't work for me. Do I call it the wrong way?

    if (!bd->BackfaceCulling(c_normal->v3, c_normal->off))  
      bd->DrawLine(c_normal->off, c_normal->off + c_normal->v3 * 10, 0);

The result is awkward:

(It doesn't even change when rotating the camera!)

However, I found a way to compute a quick & dirty Backface Culling. ^^

        Bool BackfaceCulling(const Vector& campos, const Vector& normal,  
                                  const Vector& pos) {  
          Vector delta = campos - pos;  
          return normal.Dot(campos) < (M_PI / 2.0);  
      }

This is the result:

Cheers,
-Nik

Helper

THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED

On 09/07/2012 at 06:52, xxxxxxxx wrote:

Originally posted by xxxxxxxx

Hi spedler,Hm, the method doesn't work for me. Do I call it the wrong way?
    if (!bd->BackfaceCulling(c_normal->v3, c_normal->off))        bd->DrawLine(c_normal->off, c_normal->off + c_normal->v3 * 10, 0);

I don't know, as I say I've never used this function. It looks like you're not using it correctly - you draw the line if bd->BackfaceCulling returns TRUE (i.e. the face is visible). It also depends on what is in your variable c_normal - you need the centre of the polygon and the face normal. You can get the normal with CalcFaceNormal, the centre you have to calculate yourself from the coordinates of the points which make up the polygon concerned.

Helper

THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED

On 09/07/2012 at 07:32, xxxxxxxx wrote:

Hello spedler,

right I forgot to add this. c_normal->off contains the polygon's center while ->v3 contains the normal. I've calculated myself (to resolve function-call overhead) but the values are correct. (Otherwise the drawn lines would be messed up or incorrect)

> you draw the line if bd- >BackfaceCulling returns TRUE (i.e. the face is visible).
Well, that's what I want.

Thank you,
Niklas

Helper

THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED

On 09/07/2012 at 08:46, xxxxxxxx wrote:

Sorry, I should have been clearer. In your code you are testing if BackfaceCulling() returns FALSE. That means a poly isn't visible, but then you are drawing the line. You need it the other way round. Remove the '!' before bd->BackfaceCulling.