Stepping into deep water, need advice

BlitzMax Forums/BlitzMax Programming/Stepping into deep water, need advice

wmaass

(Posted 2011) [#1]

I am creating a module for a piece of machine vision hardware. I have the dll and a header file and have made progress with accessing simple functions, no problem.

Now, there are certain other functions that I need to access but I am unsure of how to deal with them.

I can't provide the exact function or much detail about the DLL (NDA) but I'll try and describe what I am seeing.

For example there is a function in the header like so:

int getposition( float* x, float* y, float* z );

I know that this function provides x,y,z coordinates for a feature in the camera space.

From what I can gather, this function takes pointers for parameters, puts the coordinate data into those pointers and then returns an int indicating success or failure. Before I continue with too many silly questions, is my assumption reasonable? Also, how would I translate this function into my mod, is this close?

Extern
getposition:Int(x:Byte Ptr, y:Byte Ptr, z:Byte Ptr)
End Extern

skidracer

(Posted 2011) [#2]

Try this:

Extern
Function getposition:Int(x:Float Ptr, y:Float Ptr, z:Float Ptr)
End Extern

and to test pass standard BlitzMax float arrays

Last edited 2011

wmaass

(Posted 2011) [#3]

Thanks skidracer, the module compiles now. As for the test, I tried this:

Local posArray:Float[3]
Local p:Float Ptr
p = posArray
getposition(p[0], p[1], p[2])

Unable to convert from 'Float' to 'Float Ptr' on the function call.

Ideas?

Last edited 2011

wmaass

(Posted 2011) [#4]

did this, seems to work:

Local px:Float
Local py:Float
Local pz:Float

Local x:Float Ptr = Varptr px
Local y:Float Ptr = Varptr py
Local z:Float Ptr = Varptr pz

getposition(x, y, z)

skidracer

(Posted 2011) [#5]

At a guess I think the code should possibly look like this? The number 4096 should be set to maximum number of points that getposition is documented to return.


Global PX:Float[4096]
Global PY:Float[4096]
Global PZ:Float[4096]

' scan image

local n=getposition(PX,PY,PZ)

' dump results

For local i=0 until n
  DebugLog "Point "+i+":"+PX[i]+","+PY[i]+","+PZ[i]
next

Last edited 2011

Last edited 2011

wmaass

(Posted 2011) [#6]

The function getposition returns the 3D position of an object of interest, for instance a persons head.

Seems like there are a few ways to skin this cat but at least something is working, thanks to your help.