3D vertex saving
lazarus / 21-General

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lazboy10 · 2021-03-14 10:42

Hi there!

i have been working on a 3d modeler software and i have a problem with
saving the model to file.

the model is built with 2 arrays one for vertices and one for faces.
All deleted vertices have a "Deleted" value.
So when i try to save and skip the deleted vertices the face vertex
indexes get all mixed up resulting in a total mess.

I have tried to loop through all faces and change the indexes but it
just doesn't work.

i have tried everything i can think of to get it working but nothing
works. So im asking here if anyone knows how to do it, and if you
would provide some simple code to do it that would be awesome. cheers.

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dseligo · 2021-03-14 10:57

Try to save array with "Deleted" value and see if that works.
Can you show array declaration and code you use to save arrays?

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lazboy10 · 2021-03-14 11:06

It works if i keep the deleted vertices but i need to skip them...
here is some code that i tried



for skipping the deleted vertices:

VertCount := 0;
for I := 0 to Length(ModelData.Groups[0].Vertices)-1 do
if ModelData.Groups[0].Vertices.Deleted = False then
begin
  SetLength(TempVertices, VertCount+1);
  TempVertices[VertCount] := ModelData.Groups[0].Vertices;
  Inc(VertCount);
end;

this is for trying to decrease the face list indexes.

    FCount := 0;
    for V := 0 to Length(TempVertices)-1 do
    begin
      Vert := TempVertices[V];
      if Vert.Deleted = True then
      begin
        Index := V;
        for F := FCount to Length(ModelData.Groups[0].Faces) -1 do
        begin
          Face := ModelData.Groups[0].Faces[F];
          if Face.V1 = Index then
            Dec(Face.V1);
          if Face.V2 = Index then
            Dec(Face.V2);
          if Face.V3 = Index then
            Dec(Face.V3);

          ModelData.Groups[0].Faces[F] := Face;
        end;
        Inc(FCount);
      end;
    end;

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marcov · 2021-03-14 11:21

If you are not against throwing an array of integers to it

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var
indexmapping : array of integer; setlength(indexmapping,Length(ModelDa
ta.Groups[0].Vertices));VertCount := 0;for I := 0 to
Length(ModelData.Groups[0].Vertices)-1 dobeginif
ModelData.Groups[0].Vertices.Deleted = False thenbegin 
SetLength(TempVertices, VertCount+1);  TempVertices[VertCount] :=
ModelData.Groups[0].Vertices;  indexmapping[i]:=vertcount; // i is now
at current value of "vertcount"  Inc(VertCount);endelse 
indexmapping[i]:=-1; // signal deleted vertex for double checking if
neededend; then walk the faces and just do if indexmapping=-1 remove
it.

This also reduces a two dimensional (O(n^2)) walk into two linear
(O(n) ) ones.

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speter · 2021-03-14 22:24

I'd suggest simply saving the faces (after the scene settings etc),
with each face including its points (and colours etc). Then when
loading the scene rebuild the points list.

Have a look at https://forum.lazarus.freepascal.org/index.php/topic,52
526.msg387685.html#msg387685 there is a link to a project which loads
a (text file) with a 3d model; it doesn't include 'save' but it does
include 'readfromdisk()'; it might also be of interest to see a more
object oriented approach. Look at "sceneu.pas" and "hut.per".

cheers
S.

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lazboy10 · 2021-03-16 19:07

Quote from: marcov on March 14, 2021, 12:21:49 pmIf you are not
against throwing an array of integers to it

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var
indexmapping : array of integer; setlength(indexmapping,Length(ModelDa
ta.Groups[0].Vertices));VertCount := 0;for I := 0 to
Length(ModelData.Groups[0].Vertices)-1 dobeginif
ModelData.Groups[0].Vertices.Deleted = False thenbegin 
SetLength(TempVertices, VertCount+1);  TempVertices[VertCount] :=
ModelData.Groups[0].Vertices;  indexmapping[i]:=vertcount; // i is now
at current value of "vertcount"  Inc(VertCount);endelse 
indexmapping[i]:=-1; // signal deleted vertex for double checking if
neededend; then walk the faces and just do if indexmapping=-1 remove
it.

This also reduces a two dimensional (O(n^2)) walk into two linear
(O(n) ) ones.

Hey,
What do you mean by "then walk the faces and just do if
indexmapping=-1 remove it." can you show me with code how do it? i
have tried a few things with the integer list, but nothing that's
worked.