Programming Forums > Application Development > Assembly

Klarre · Nov 7th, 2005, 1:30 PM

I have a problem with floats and doubles.

I wanted to put a camera in my OpenGL scene. But when
I added the gluLookAt function, the program did'nt started
anymore.

I was using this code, and simply made a call like

(Toggle Plain Text)

_gluLookAt eyex, eyey, eyez, centerx, centery, centerz, upx, upy, upz

in my draw function.
These variables are created like this:

(Toggle Plain Text)

eyex dd 0.0

(Toggle Plain Text)

_gluLookAt macro A1, A2, A3, A4, A5, A6, A7, A8, A9
	push A9
	push A8
	push A7
	push A6
	push A5
	push A4
	push A3
	push A2
	push A1
	call gluLookAt
endm

I guessed that the problem was that the gluLookAt function expects 64 bits doubles,
instead of 32 bits floats. I tried my assumption by pushing twice as much on the stack.
Then the program started again, but with wrong values to gluLookAt of course.

How shall I solve this problem? How do I convert my floats to doubles? Is there
a simple way of doing this?

I am not an assembly guru, so try keeping the answears as clean as possible

Thanks

/Klarre

Polyphemus_ · Nov 7th, 2005, 1:36 PM

Maybe this page helps: http://www.osdata.com/topic/language/asm/convert.htm

Good luck

Klarre · Nov 7th, 2005, 2:39 PM

Thanks for the link! It took me back on track again.

But...

I got that I should use the cdq instruction to extend the eax to edx. Right?

Am I thinking correct if I try using this rewritten code instead of the old one?

(Toggle Plain Text)

_gluLookAt macro A1, A2, A3, A4, A5, A6, A7, A8, A9
	mov eax, A9
	cdq
	push eax
	push edx

	mov eax, A8
	cdq
	push eax
	push edx

	...

	mov eax, A1
	cdq
	push eax
	push edx

	call gluLookAt
endm

Klarre · Nov 7th, 2005, 4:12 PM

Problem solved...

iignotus · Nov 7th, 2005, 6:04 PM

Mind posting the solution to help others?

Klarre · Nov 8th, 2005, 5:09 AM

I solved it using constants. It is a solution so far. And next step is to use double variables instead, so I can move the camera around in real time.

The original function used

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void gluLookAt(GLdouble eyeX, GLdouble eyeY, GLdouble eyeZ,
               GLdouble centerX, GLdouble centerY, GLdouble centerZ,
               GLdouble upX, GLdouble upY, GLdouble upZ);

In C++ the code would look like this:

(Toggle Plain Text)

double eyez = 45.0;
double upy  = 1.0;

gluLookAt(0, 0, eyez, 0, 0, 0, 0, upy, 0);

Rewritten in assembly it looks like this:

(Toggle Plain Text)

_45d0 equ 40468000h  ; eyez
_45d1 equ 0
_1d0  equ 1072693248 ; upy
_1d1  equ 0

;; upx, upy, upz pushed on the stack
push 0
push 0
push _1d0
push _1d1
push 0
push 0

;; centerx, centery, centerz pushed on the stack
push 0
push 0
push 0
push 0
push 0
push 0

;; eyex, eyey, eyez pushed on the stack
push _45d0
push _45d1
push 0
push 0
push 0
push 0

call gluLookAt

Nov 7th, 2005, 1:30 PM	#1
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 288 Rep Power: 4	Floats to doubles I have a problem with floats and doubles. I wanted to put a camera in my OpenGL scene. But when I added the gluLookAt function, the program did'nt started anymore. I was using this code, and simply made a call like (Toggle Plain Text) _gluLookAt eyex, eyey, eyez, centerx, centery, centerz, upx, upy, upz _gluLookAt eyex, eyey, eyez, centerx, centery, centerz, upx, upy, upz in my draw function. These variables are created like this: (Toggle Plain Text) eyex dd 0.0 eyex dd 0.0 (Toggle Plain Text) _gluLookAt macro A1, A2, A3, A4, A5, A6, A7, A8, A9 push A9 push A8 push A7 push A6 push A5 push A4 push A3 push A2 push A1 call gluLookAt endm _gluLookAt macro A1, A2, A3, A4, A5, A6, A7, A8, A9 push A9 push A8 push A7 push A6 push A5 push A4 push A3 push A2 push A1 call gluLookAt endm I guessed that the problem was that the gluLookAt function expects 64 bits doubles, instead of 32 bits floats. I tried my assumption by pushing twice as much on the stack. Then the program started again, but with wrong values to gluLookAt of course. How shall I solve this problem? How do I convert my floats to doubles? Is there a simple way of doing this? I am not an assembly guru, so try keeping the answears as clean as possible Thanks /Klarre

Nov 7th, 2005, 2:39 PM	#3
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 288 Rep Power: 4	Thanks for the link! It took me back on track again. But... I got that I should use the cdq instruction to extend the eax to edx. Right? Am I thinking correct if I try using this rewritten code instead of the old one? (Toggle Plain Text) _gluLookAt macro A1, A2, A3, A4, A5, A6, A7, A8, A9 mov eax, A9 cdq push eax push edx mov eax, A8 cdq push eax push edx ... mov eax, A1 cdq push eax push edx call gluLookAt endm _gluLookAt macro A1, A2, A3, A4, A5, A6, A7, A8, A9 mov eax, A9 cdq push eax push edx mov eax, A8 cdq push eax push edx ... mov eax, A1 cdq push eax push edx call gluLookAt endm

Nov 8th, 2005, 5:09 AM	#6
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 288 Rep Power: 4	I solved it using constants. It is a solution so far. And next step is to use double variables instead, so I can move the camera around in real time. The original function used (Toggle Plain Text) void gluLookAt(GLdouble eyeX, GLdouble eyeY, GLdouble eyeZ, GLdouble centerX, GLdouble centerY, GLdouble centerZ, GLdouble upX, GLdouble upY, GLdouble upZ); void gluLookAt(GLdouble eyeX, GLdouble eyeY, GLdouble eyeZ, GLdouble centerX, GLdouble centerY, GLdouble centerZ, GLdouble upX, GLdouble upY, GLdouble upZ); In C++ the code would look like this: (Toggle Plain Text) double eyez = 45.0; double upy = 1.0; gluLookAt(0, 0, eyez, 0, 0, 0, 0, upy, 0); double eyez = 45.0; double upy = 1.0; gluLookAt(0, 0, eyez, 0, 0, 0, 0, upy, 0); Rewritten in assembly it looks like this: (Toggle Plain Text) _45d0 equ 40468000h ; eyez _45d1 equ 0 _1d0 equ 1072693248 ; upy _1d1 equ 0 ;; upx, upy, upz pushed on the stack push 0 push 0 push _1d0 push _1d1 push 0 push 0 ;; centerx, centery, centerz pushed on the stack push 0 push 0 push 0 push 0 push 0 push 0 ;; eyex, eyey, eyez pushed on the stack push _45d0 push _45d1 push 0 push 0 push 0 push 0 call gluLookAt _45d0 equ 40468000h ; eyez _45d1 equ 0 _1d0 equ 1072693248 ; upy _1d1 equ 0 ;; upx, upy, upz pushed on the stack push 0 push 0 push _1d0 push _1d1 push 0 push 0 ;; centerx, centery, centerz pushed on the stack push 0 push 0 push 0 push 0 push 0 push 0 ;; eyex, eyey, eyez pushed on the stack push _45d0 push _45d1 push 0 push 0 push 0 push 0 call gluLookAt

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Nov 7th, 2005, 1:36 PM	#2
Polyphemus_ Expert Programmer Join Date: Aug 2005 Location: Rotterdam, the Netherlands Posts: 942 Rep Power: 3	Maybe this page helps: http://www.osdata.com/topic/language/asm/convert.htm Good luck

Nov 7th, 2005, 4:12 PM	#4
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 288 Rep Power: 4	Problem solved...

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Programming Forums > Application Development > Assembly

Floats to doubles