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8 (9%)

Functions

4 (4.5%)

Basic object-oriented programming

30 (33.7%)

A bit more advanced OOP (Composition, Operator overloading, Inheritance, Virtual Functions)

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Total Members Voted: 89

[ILikePie]

Spoiler (click to show/hide)

Is there an easy way of doing if(a < b < c){} in C++?
Right now I think it's doing a (a<b == true and true == 1) and ( 1 < c ).

I'm trying to ascertain whether all 8 corners of a cube have a "value x" that is above or below a threshold, and I want to take action as soon as one of them is "on the other side".


Right now I've got this:

Code: [Select]

   
//cur2 is the length of the side of the cube, goOn is a bool, false by default
    float a = -9999.f;
    float b = cutoff;
    if(sample(x, y, z) < cutoff){ a = cutoff; b = 9999.f; }

    if(!goOn && (a<sample(x+cur2, y, z)<b)){goOn = true;}
    if(!goOn && (a<sample(x, y, z+cur2)<b)){goOn = true;}
    if(!goOn && (a<sample(x+cur2, y, z+cur2)<b)){goOn = true;}
    if(!goOn && (a<sample(x, y+cur2, z)<b)){goOn = true;}
    if(!goOn && (a<sample(x+cur2, y+cur2, z)<b)){goOn = true;}
    if(!goOn && (a<sample(x+cur2, y+cur2, z+cur2)<b)){goOn = true;}
    if(!goOn && (a<sample(x, y+cur2, z+cur2)<b)){goOn = true;}
Any good ideas?

I'd drop those braces, they look ugly.

Code: [Select]

if(!goOn && (a<sample(x+cur2, y, z)<b)){goOn = true;}
vs
if(!goOn && (a<sample(x+cur2, y, z)<b)) goOn = true;


[Siquo]

I'd drop those braces, they look ugly.

Ah, that solved everything! [/sarcasm]

I like em. Everything needs to be enclosed, or my scanning (reading the code w/o reading it) is severely hampered.

To do a<b && b<c I need:

Code: [Select]

if(!goOn){
  float b = sample(x,y,z);
  if(a<b && b<c){
    goOn = true;
  }
}times 8. That's a line-inflation of 600%. I want to call "sample" as few times as possible, and keep stuff clean and small if possible. There's also the possibility that there's no way around this

I've got it! You can assign inside an expression!

Code: [Select]

float b; // can be reused
if(!goOn && (a<(b=sample(x+cur2, y, z)) && b<c))Doesn't improve readability, but it works.

[alway]

Just wondering, but are said cubes being compared lined up with the world axis or are they rotated at different angles?

[Siquo]

Axis-aligned for now, but does it matter?

[Virex]

times 8. That's a line-inflation of 600%. I want to call "sample" as few times as possible, and keep stuff clean and small if possible. There's also the possibility that there's no way around this

That depends. If you're going for readability you could just write your own (inlined) comparer functions that takes a, b and c as it's parameters and use that as the body of the if-expression.

[Siquo]

Yeah, that's what I'd do if I was doing it nice.
Solution works though. Now to find the "gaps"...

[eerr]

Ehh, you got it before me. I should read more carefully.

[Virex]

It does, but I'm not sure what you'd want to do with them here?

[qwertyuiopas]

Try

Code: [Select]

inline int is_between(float test, float low, float high)
{
    return test > low && test < high;
}

[Siquo]

Yeah, that's even cleaner. It already works, though

Edit: except that I don't use non-member functions. I don't know if I should, I never really had to.

In case anyone cares, what I needed it for:

Spoiler (click to show/hide)

Yes, it's a peanut! And I did manage to make the "merging area" between the two spheres rounded instead of "flat" cylindric.

[eerr]

Lovely, but what willl you do with it?

[Siquo]

... making the most awesomest game EVER? 

This is for true 3D terrain generation (instead of a 2d terrain with a heightmap ), and (hopefully) easy and quick terrainmodification on any scale. Think... minecraft without cubes. With (almost) procedurally generated (almost) everything. Once I get there, the sky is the limit. Or the center of the earth is the limit, depending on which way you build/dig.

[eerr]

... making the most awesomest game EVER? 

This is for true 3D terrain generation (instead of a 2d terrain with a heightmap ), and (hopefully) easy and quick terrainmodification on any scale. Think... minecraft without cubes. With (almost) procedurally generated (almost) everything. Once I get there, the sky is the limit. Or the center of the earth is the limit, depending on which way you build/dig.

How will you handle terrain deformations?

[Rose]

by the looks of things, that be a voxel engine.

[Siquo]

Almostish.
I'm using the marching cubes algorithm recommended to me by Japa.

Spoiler (click to show/hide)

All "matter" is merely a function: sample(x,y,z). For instance, my current hilly landscape is a simple

Code: [Select]

if(y<sin(10*x)+sin(10*z)) return 100.f;in 2D it'd look like this:

Code: [Select]

0000000000000
0011000011000
0111100111100
1111111111111The algorithm looks for the edge of this "blob" of 100's.

This means that I can draw that same landscape using vertices of 10 or vertices of 0.001.

Now, if I add multiple shapes together (such as the peanut, which is two spheres), they will "merge", if I let the function degrade softly at the edges (currently using a sine to degrade from 100 to 0, softness and transition are parameters as well). This is nice for construction design. However, I could also add negative numbers. If I make a cylinder with value -100.f, it will show as a hole through the peanut (or ground or whatever).

Code: [Select]

0000000000000
0000000011000
0100100111100
1100111111111
  ^^ Hole is here, the zeroes above are actually -1 but that doesn't matter
This sampling is done per object, so it's not as if it's one giant world made of putty, there's hard edges as well for players/plants/etc. So it's not exactly voxels, as there's no lower or upper limit to the resolution.