[SDL] triangles & aspects

Clangray clangray at fastmail.com
Fri Mar 24 14:48:01 PDT 2017


I didn't articulate that very well but thats more of what I am needing:
getting the 3rd point.


--

  Gray Family

  clangray at fastmail.com







On Fri, Mar 24, 2017, at 05:03 PM, Clangray wrote:

> I know the math, its just if I want to place an equilateral triangle
> in several different places on the screen I'd like to know what
> anybody has done before me in this situation: are there any automated
> functions in SDL2?
> 

> *Most importantly they need to be filled triangles. How do I fill
> traingles?? : )*
> 

> --

>   Gray Family

>   clangray at fastmail.com

> 

> 

> 

> On Fri, Mar 24, 2017, at 02:58 AM, Sanette wrote:

>> Le 23/03/2017 à 22:19, speartip a écrit :

>> > Hi, > > I am endeavoring to put some simple triangles in my screen.
>> > The SDL wiki gives an example of - yes - connecting 3 drawlines. Am
>> > I overlooking something or do these lines have to be arrived at
>> > mathematically or hardcoded to know what anchoring coordinates they
>> > must belong to form the triangle. I don't see a function to make
>> > the triangle for you. This becomes rather labor intensive to create
>> > your triangle. Also once made, if your aspect ratio changes the
>> > lines of the triangle will have to be recalculated to maintain the
>> > equality of the angles. I can make a function to correct, no prob.
>> > > > Before venturing out on some crazy triangle project, just
>> > wanted to know whether I was missing some piece of info. > > >
>> > _______________________________________________ > SDL mailing list
>> > > SDL at lists.libsdl.org >
>> > http://lists.libsdl.org/listinfo.cgi/sdl-libsdl.org
>> 

>> 

>> Hi

>> 

>> your question is not terribly clear. Mathematically, a triangle is

>> just given by 3 points, so there is no problem. (By the way do
>> you want
>> simple triangles or filled triangles ? Do you want anti-aliasing ?)

>> 

>> Maybe what you mean in fact is an equilateral triangle: all
>> sides have
>> same length. Then, yes there is some math behind this. There are many
>> possibilities. Either you compute the position of the third point

>> given the first two.  Or it might be easier to draw a horizontal

>> segment (the base of the triangle), and then use SDL_RenderCopyEx to
>> copy+rotate by 60° to obtain the two other sides.

>> 

>> -- 

>> sanette -- full_time_linux

>> 

>> 

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> 

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