[gameprogrammer] RES: Re: RES: Re: DirectX Line and Triangle
- From: "Edilson Vasconcelos de Melo Junior" <dirso@xxxxxxxxxxxxxxxxxx>
- To: <gameprogrammer@xxxxxxxxxxxxx>
- Date: Mon, 14 Jul 2008 20:40:36 -0300
The triangle is really a flat triangle, it's just something to indicate a
path. And the line segments do have x,y and z values. I work on this project
like google earth 3d client and my task is to draw lines representing
streets and make triangles over them pointing the allowed driving way.
Thanks,
Dirso
De: gameprogrammer-bounce@xxxxxxxxxxxxx
[mailto:gameprogrammer-bounce@xxxxxxxxxxxxx] Em nome de Alan Wolfe
Enviada em: segunda-feira, 14 de julho de 2008 19:22
Para: gameprogrammer@xxxxxxxxxxxxx
Assunto: [gameprogrammer] Re: RES: Re: DirectX Line and Triangle
the triangle you want to put on the lines, do you want it to be 3
dimensional (ie a pyramid, not a triangle?) or do you want it to just really
be a triangle.
also, when you say you are in 3d do you mean that your line segments all
have different X,Y and Z values? or are they all on the same Z value?
On 7/14/08, Edilson Vasconcelos de Melo Junior <dirso@xxxxxxxxxxxxxxxxxx>
wrote:
Hi,
I'm in 3d. can you help me a little more?
Thank you very much for your help,
Dirso
De: gameprogrammer-bounce@xxxxxxxxxxxxx
[mailto:gameprogrammer-bounce@xxxxxxxxxxxxx] Em nome de Alan Wolfe
Enviada em: segunda-feira, 14 de julho de 2008 17:38
Para: gameprogrammer@xxxxxxxxxxxxx
Assunto: [gameprogrammer] Re: DirectX Line and Triangle
Hey Dirso,
Here's a plan of attack (assuming you are in 2d)
Calculate the normal of the line segment to get a normalized vector
perpendicular to the line, this will be useful to figure out the vertices
for the flat back side of the triangle. Call this NX and NY.
Calculate the normalized vector of the line, call this LX and LY.
Find the midpoint of the line call this MX and MY.
Figure out how wide and how tall you want the triangle to be, call this
TWidth and THeight.
If you do the above, here's how to find each of the 3 vertices for the
triangle for each line:
Vertex 1:
*start at the midpoint
*subtract LX,LY multiplied by TWidth/2
*add NX,NY * THeight/2
Vertex 2:
*start at the midpoint
*add LX,LY * TWidth/2
Vertex 3:
*start at the midpoint
*subtract LX,LY multiplied by TWidth/2
*subtract NX,NY * THeight/2
That will give you the vertices in a clockwise order, so watch out for back
face culling if you have clockwise culled (:
On 7/14/08, Edilson Vasconcelos de Melo Junior <dirso@xxxxxxxxxxxxxxxxxx>
wrote:
Hi,
I have a CustomVertex.PositionColored[] object that represents a line and I
use the DrawUserPrimitives(PrimitiveType.LineStrip, this.linePoints.Length -
1, this.linePoints); to draw it on screen
Now I need to draw a small triangle aligned to each line segment and one of
each vertex must "pointy" to the finish point of the segment. How can I do
that?
Something like the attached picture, but not that ugly.
Thanks,
Dirso.
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