Computer Graphics Forum RSS Feed (Replies Included)

Re: Vertical dotted lines running on screen

Tue, 27 Oct 2009 03:24:18 -0700

don't move your monitor while the power supply is on and your monitor is in working mode.

Re: Vertical dotted lines running on screen

Mon, 26 Oct 2009 03:03:48 -0700

don't place your monitor near a any metal, it would be affect your display by strong magnetic field. also it cause by the supplied power fluctuated.

Inverse homogeneous transformation

Wed, 21 Oct 2009 12:05:54 -0700

Hello, I have a question about inverse homogeneous transformation. while i am reading a book "Introduction to Robotics mechanics and control" there is an example which says that: We have two frames A and B, Frame A is deduced from A by rotating A 30 degree and translating it 4 by x and 3 by y so the matrix of the transformation of B relative to A is:
0.866 -0.5 0 4
0.5 0.866 0 3
0 0 1 0
0 0 0 1
The question is to find A relative to B so i said that the rotation will be -30 and the x=-4 and the y=-3 so it will be:
0.866 0.5 0 -4
-0.5 0.866 0 -3
0 0 1 0
0 0 0 1
but actually it is not the result they had a rule that changes the translation part(last column) by multiplying the matrix rotation of A relative to B by the translation vector and the result is inserted in the last column.
Please can any one help?
Hani Almousli......

Re: Can someone explain the DCT to me ??

Fri, 02 Oct 2009 04:45:28 -0700

Have a look at following two links to get an idea of the combination between JPEG compression and DCT

JPEG - JPEG Image Compression Explained

DCT - Discrete Cosine Transformation (DCT)

Drawing halo outlines around objects

Sun, 13 Sep 2009 05:15:24 -0700

Hi,

I'm developing an OpenGL application in the VxWorks. The display is supposed to be able to generate an outline around objects drawn. The outline has to be one pixel thick on the outer surface and inner surface of the object (for hollow objects) and on the outer surface for filled objects.

Is there any efficient way to create this outline during run-time? I'm facing problems for some of the symbols because these symbols are generated run-time based on instructions from a database. I then create display lists to draw these symbols.

I'm relatively new to openGL programming and am not very proficient in programming in OpenGL. Please drop any suggestions or solutions you may have. Thanks.

A CreateDevice Direct3D Error...

Sun, 02 Aug 2009 10:07:23 -0700

Hello, i'm new here. I hope to get along well...

Well, here's my problem. When i try to open the Dance editor for Dance X Mixer, it gives my this error:

Can someone help me with this? The character editor and dress editor work fine for me.

Thanks.

Re: Coding 2D graphics in C, to be portable

Tue, 28 Jul 2009 08:40:40 -0700

Write all your functions so they take a graphics context as the first argument.

The graphics context should contain the members

int width;
int height;

long (*getpixel)(int x, int y, void *ptr);
void (*putpixel)(int x, int y, long color, void *ptr);
void *ptr;

width and height are self-explantory. getpixel and putpixel anre fuunction pointers which read and write single pixels to the screen. ptr is a general-purpose hook so the functions don't have to rely on global data.

These days you can pretty much guarantee truecolour graphics. However you'll have to add extra members if you wish to support paletted images nicely.

Using this abstraction layer, all your algorithms can work perfectly portably.

Re: Graphics in C

Tue, 28 Jul 2009 08:34:00 -0700

Yes, but you need a library.

However getpixel() and putpixel() or whatever equivalent exists is all you need. The rest can be built up out of pure logic. On a modern computer C is fast enough to do the most intricate 2D graphics in a single frame.

You can look up the algorithms themselves in books like Graphics Gems, or just do a websearch on the anme.

Graphics in C

Tue, 28 Jul 2009 06:58:09 -0700

can i draw figures(lines,circles etc) in all 4 quadrants
with DDA /Bresenhamms in C language?
plz reply.

D3D projection matrix

Sun, 26 Jul 2009 04:28:51 -0700

i am looking at the sdk and learning how to pick , well i am stuck understanding this
rayDir.x = v1.x*m._11 + v1.y*m._21 + v1.z*m._31;
rayDir.y = v1.x*m._12 + v1.y*m._22 + v1.z*m._32;
rayDir.z = v1.x*m._13 + v1.y*m._23 + v1.z*m._33;

what is happening on the matrix after you SetTransform?, what does each element mean

They hacked my password. Slap me!

Re: Coding 2D graphics in C, to be portable

Mon, 29 Jun 2009 02:50:28 -0700

No, I totally get it, making a library. My only intentions were to be educational; I was never planning on distributing it (or possibly finising it =]). Anyway, I could never even dream of making a library as good as OpenGL, or others. =] Thanks!

Re: Coding 2D graphics in C, to be portable

Sun, 28 Jun 2009 16:23:34 -0700

Duplicate post deleted.

Re: Coding 2D graphics in C, to be portable

Sun, 28 Jun 2009 16:23:32 -0700

Hi and welcome!

I'm not exactly sure what you might need, but you're probably looking for something like SDL or OpenGL:
http://www.libsdl.org/
http://en.wikipedia.org/wiki/OpenGL

I wonder why you would want to make your own library for this. It's great for learning, but not very practical when other libraries already exist that do a great job at it. I also don't think it's sensible to make a library that does everything (at least not all by yourself). That would be reinventing the wheel. Not to discourage or anything, just wondering :)

Coding 2D graphics in C, to be portable

Sun, 28 Jun 2009 11:14:55 -0700

Hello all,

Well, this is my first post in Programmer's Heaven.
Recently, I began developing my own programming library, written in C. When I got to the graphics, I became stumped, because I want the library to be portable, on both OS, and hardware. Every way I think of creating graphics, a different architecture or software platform is excluded. For example, if I used the Windows API, only windows, or possibly Wine can run it; if I use assembler, only one architecture can run it, and I REALLY don't want to re-write the assembly routines for multiple architectures (don't think I could do it for many at all =]...). Any ideas?

Re: Vertical dotted lines running on screen

Thu, 25 Jun 2009 06:07:40 -0700

It is not a software problem, but rather a hardware malfunction. You need to fix your laptop (replace monitor) or get another one. Choose the less costly "fix".

How many years you have been using your laptop?

Vertical dotted lines running on screen

Thu, 25 Jun 2009 00:24:36 -0700

hi everyone,

the problem i am facing is screen mulfunction. c o l o r e d vertical dotted lines are running on my compaq laptop screen. it just started a week before with just one line which i ignored. then after 2-3 days one more line appeared. next day one more and now 4 lines are there. someone told that lines will go on increasing. what should i do? please help....

Re: Opening bitmap images in C/C++ as matrices

Wed, 24 Jun 2009 09:51:14 -0700

Hi

I am new to C++.Thanks a lot for the code. The concept is very useful. However, when I compile the code it gives the following error

'fread' : cannot convert parameter 1 from 'void' to 'void *'
1>        Expressions of type void cannot be converted to other types"

This is because the "Array" parameter is of unsigned char type and not array type and the fread syntax is to store it in void * pointer type. Kindly tell how to rectify this problem.

thanks a lot in advance

Re: what is a Z buffer?

Wed, 24 Jun 2009 09:30:20 -0700

I have similar question. I have one 3D object and I meshed it. The outside boundaries has triangular mesh. I need to find which triangle can be seen from other triangle. Can I use Z buffer algorithm. I am using MATLAB.
Thanks
serap

Rotation of a 2D image without changing the size

Sat, 20 Jun 2009 04:47:41 -0700

When we use rotation matrix transformation
to rotate a 2D image about a point, the size
of the image changes except for a rotation of
90,180, 270 and 360 degrees. Although
inbuilt function is written in matlab and
photoshop, the size of the image changes
after rotation in boththe softwares.
This is because, the pixel
positions are integer values, and when the
transformation is applied to each and every
piel value of the image, more than one
pixel is transformed to the same position (
because of rounding off)in the rotated image
and hence some of the pixel intensities are
overwitten .
How to overcome this problem?

convert 3d object to its height field

Thu, 18 Jun 2009 07:07:57 -0700

can anyone give me some suggestions : how to how to convert 3d object to its height field?

thanks a lot

GIF Negative? (Solved)

Sun, 14 Jun 2009 09:49:43 -0700

I am trying to decode a GIF image file format. The GIF file format using LZW can return negative references. If you simply use absolute value on these references you get the "GIF Negative" of the image. The GIF negative is not what I expected. It is not just 255-x to get the back to normal. The best way to describe this is to try adding the color into ms paint (or any other software) and clicking negative with the file format set to GIF. Here is an example.
NORMAL -> Negative
RRR GGG BBB -> RRR GGG BBB
255 000 000 -> 255 204 102
000 255 000 -> 255 204 051
000 000 255 -> 255 153 255
255 255 255 -> 255 153 102
I am trying to convert the "GIF Negative" back to "GIF Normal".
Any ideas of where I could find the answer?

Edit: I found the answer. I will post it here. You can delete this post or save it for future reference.
The way "GIF Negative" works is, after you decode the image but before you reference it, you do this:
if (Current reference)<0
(new reference)=(total references)+(Current reference(should be negative number only!))
Note: Do this after you decode using LZW (if needed).

Get position array following a line

Fri, 12 Jun 2009 06:21:35 -0700

Poll:

	0 votes
	0 votes

I'm trying to do basic GDI animations with bitmaps. What I want to do is make a bitmap move towards a point.
I want the bitmap move in small steps towards this point.
So what I really want to know is how I can get a Point array of all the small steps to this position so I can redraw anything on each position.

I think if I where to make this a function it would have this look. I can't figure out how to make the logic.

Point[] GetLineSteps(Point startxy, Point stopxy)
{

Return LineSteps;
}

Appreciate your help.

Re: Accessing the QuickTime frame buffer

Thu, 21 May 2009 04:59:20 -0700

and did you solve it ?
wich language do you use ?

how to make this graphic in C++

Sat, 16 May 2009 15:29:50 -0700

i'm training in graphic's programming.
can you help me to make the source code from picture above?
i wanna to learn it.
thanks

OpenGL graphics editor project

Fri, 15 May 2009 00:33:23 -0700

I need the code for a graphics editor using OpenGL...This is part of my engg subject....
Please do send me the code immediately....as its very urgent...

I should be able to run the program in microsoft visual studio...

Please do help me...