Thanks a lot! Anthony, I will take a look and tell you the results after weekend.
Greetings! Thanks again. On Thu, Apr 23, 2015 at 5:53 PM, Anthony Tan <[email protected]> wrote: > Bit quiet at work today while I wait for a shot to bubble through, so > thought I'd do a quick writeup > > *TL;DR - it's not geometric distance, it's the focal plane distance (as > in, the distance along the camera axis to the focal plane that contains the > point you're looking at) - *if anyone wants I can do up a sketch and a > decenter write up, just yell, this was me poking around in maya more than > the maths > > > *As a simple proof/demo:* > - create a camera, create a polycube. > - set the transform on the polycube to be -1 on Z. Distance will be 1. > - set the transform on the polycube to be -1 on Z, and 1 on X. Distance is > still 1, even though we have clearly changed the geometric distance, it's > still sliding on the focal plane 1 unit away from the camera. > - move your camera wherever you want on the X/Y plane. Distance is still > 1, because you're moving on the plane. > - Rotate your camera. Distance changes because by rotation, you're > shifting your focal plane around > > > *And the longwinded answer..* > Under the hood in Maya, I suspect the object's bounding box center is > being used (I thought it was the worldMatrix at first, but you can see this > isn't the case trivially by taking a cube, and moving all the verts. > Distance will change, even though the worldMatrix is static). Disclaimer - > I've only done limited testing so you might find a novel case where this > doesn't hold, but the problem is more for you to figure out what point you > want to test. > > I am pretty sure this is the case in the HUD however, because it makes > sense AND it explains the funny quirk that a camera is always apparently > 0.057 units away from itself - the camera's bbox center happens to be > [0,0.210,-0.057] units in local space offset and since it's in local space > the only distance we care about is the traversal along the cam normal which > is -Z, and 0.057 units. Tada! :D > > > # here's some sample code to illustrate, more verbose than usual by way of > # documentation - we use PyMEL here at the office by the way, but that > doesn't > # change the principles > > import pymel.core as pm > > # select camera, and apply the worldMatrix to the -Z basis vector to get > the > # perturbed camera normal. this will accommodate scale/rotate/skew if you > really > # really wanted to do that, and because we're using the WM it should > manage > # all manner of grouping etc etc > # (camera points down -ve Z axis unless you've done something *incredibly* > funky) > > cam = pm.PyNode('camera1') # just selecting the camera I have here > cam_normal = cam.getAttr('worldMatrix').transpose() * > pm.dt.Vector([0,0,-1]) > # Transpose to switch between row vs col major w/pymel kindly mangling > # the vector with an implicit zero element in position 4 I believe. > # You probably want to rewrite this for MVectors if you're happier with > them > > cam_normal.normalize() > cam_position = cam.getAttr('worldMatrix').translate > # do NOT use center, it will be wrong even if you account for the parent > > # this is where you'd want to start to loop over your object list > distance_object = pm.PyNode('pCube2') > object_vector = distance_object.getAttr('parentMatrix').translate + > distance_object.getAttr('center') - cam_position > > # GOTCHA: the .center attribute folds in the local object space transform, > # but won't give you parent level transforms so you need to do that > explicitly > # if you use this approach style. > > print object_vector.dot(cam_normal) > # project the object vector onto the camera normal (yay for dot products) > to > # find out how may units along it we are. > # vector and normal point away, so +ve numbers are in front, and -ve are > behind. > > > -Anthony > > > > On Wed, Apr 22, 2015, at 08:27 PM, Macbeth R. wrote: > > Does somebody know how the Distance From Camera info in the Heads Up > Display is being query? > > I can´t find the script inside the maya folder, it is a pre script but is > not being show in iniHUDScripts.mel or iniHUD.mel is > named: HUDObjDetDistFromCam > > I try different ways of getting the same value, xform, translate, center, > bounding box, none is giving me the same numbers as the HUD gives me, > besides, I had to use different method for different objects (alembics, > plugin caches like yeti fur, arnold standins) but the HUD seems to be > always right doesn't matter which kind of object you select, how is this > being achieved? > > I know I can query the HUD result directly from there, but I had to select > every object before doing that, and turn on Object Details in HUD > > Can I call the procedure HUD is using, directly from mel or python? > > Some examples, : > > > import maya.cmds as cmds > import maya.OpenMaya as om > import maya.OpenMayaUI as mui > > #-------------------------- HUD Distance from Camera (you need to turn on > Object Details) > > print(cmds.headsUpDisplay("HUDObjDetDistFromCam", q=1, sr=1)) > > #------------------------- X FORM > P1 = cmds.xform("camara", q=1, ws=1, t=1) > P2= cmds.xform(cmds.ls(sl=1), q=1, ws=1, t=1) > v1, v2 = om.MVector(*P1), om.MVector(*P2) > distanceFromCamera=om.MVector(v2-v1).length() > print "Distancia", distanceFromCamera > > #------------------------- TRANSLATE > P1 = cmds.getAttr("camara.translate") > P2= cmds.getAttr(cmds.ls(sl=1)[0]+".translate") > v1, v2 = om.MVector(*P1[0]), om.MVector(*P2[0]) > distanceFromCamera=om.MVector(v2-v1).length() > print "Distancia", distanceFromCamera > > #------------------------- CENTER > P1 = cmds.getAttr("camara.translate") > P2= cmds.getAttr(cmds.ls(sl=1)[0]+".center") > v1, v2 = om.MVector(*P1[0]), om.MVector(*P2[0]) > distanceFromCamera=om.MVector(v2-v1).length() > print "Distancia", distanceFromCamera > > > -- > You received this message because you are subscribed to the Google Groups > "Python Programming for Autodesk Maya" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/python_inside_maya/7be9473d-745e-4c13-b892-69058db807f1%40googlegroups.com > <https://groups.google.com/d/msgid/python_inside_maya/7be9473d-745e-4c13-b892-69058db807f1%40googlegroups.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > > > > -- > You received this message because you are subscribed to the Google Groups > "Python Programming for Autodesk Maya" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/python_inside_maya/1429804387.3081289.257639721.409B9198%40webmail.messagingengine.com > <https://groups.google.com/d/msgid/python_inside_maya/1429804387.3081289.257639721.409B9198%40webmail.messagingengine.com?utm_medium=email&utm_source=footer> > . > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Python Programming for Autodesk Maya" group. 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