rotation

问题 I'm trying to obtain the camera rotation on various axis in OpenGL (but using Java, LWJGL, and jME specifically). The camera object allows me to get the direction as a Vector3f, but this doesn't seem to work to get the componentised rotation; each axis appears tied to another axis. I found that toAngleAxis with the angle component with offset was a quick hack, but doesn't work properly in most situations. I'm not so good at maths unfortunately, otherwise I may have been able to work out this

问题 How can I rotate an Bitmap a given number of degrees while maintaining the area of the original bitmap. ie, what I rotate a bitmap of Width:100,Height:200, my end result will be a bigger image but the rotated portion will still have an area of 100*200 回答1: The graphics transform function is perfect for this. Create a new bitmap of the size you want, create a graphics object based off that bitmap, apply the transform then draw onto the canvas (graphics.drawimage(original_image)). Here is a

问题 I have a rectangle in SVG that I need to rotate on a pivot from a specific point. The best way I can see to do this is transform to the xy of the pivot, rotate the degree, and then transform again. The problem is the xy of the second transform. I assume its going to take cos and sin to some extent, just not sure where or why. * | | | would rotate -90degrees to *--- Maybe im looking at this the wrong way, can anyone clearify? 回答1: If you use the SVG transform attribute rather than trying to

问题 what is the difference between placing glRotatef() after glMatrixMode(GL_PROJECTION); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glRotatef(red, green, blue); and placing glRotatef() after glMatrixMode(GL_MODELVIEW); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glRotatef(red, green, blue); 回答1: From documentation: glMatrixMode() specifies which matrix is the current matrix. GL_MODELVIEW - Applies subsequent matrix operations to the modelview matrix stack. GL_PROJECTION - Applies

问题 I'm playing with OpenGL ES on iPhone and I'm trying to rotate a model by panning with the finger. I discovered the open source app Molecules that let's you do that and I'm looking at that code, but when it comes to rotate a model of mine I'm able to rotate it only around a point distant in the space (like it was in orbit as a satellite and I am the fixed planet). Any suggestion on what can be wrong? I can post the code later , maybe on demand (many lines) For the most part refer to Molecules

问题 I'm playing with OpenGL ES on iPhone and I'm trying to rotate a model by panning with the finger. I discovered the open source app Molecules that let's you do that and I'm looking at that code, but when it comes to rotate a model of mine I'm able to rotate it only around a point distant in the space (like it was in orbit as a satellite and I am the fixed planet). Any suggestion on what can be wrong? I can post the code later , maybe on demand (many lines) For the most part refer to Molecules

问题 I'm playing with OpenGL ES on iPhone and I'm trying to rotate a model by panning with the finger. I discovered the open source app Molecules that let's you do that and I'm looking at that code, but when it comes to rotate a model of mine I'm able to rotate it only around a point distant in the space (like it was in orbit as a satellite and I am the fixed planet). Any suggestion on what can be wrong? I can post the code later , maybe on demand (many lines) For the most part refer to Molecules

问题 I am having some issues with a PDF containing a rotation property created by a Xerox scanner. The below function was originally created to scale the height of an input PDF by the amount given by the variable scaleHeight. This works fine for input documents without rotation. When testing a document with a 270 degree rotation, I found that the rotation property which would have made the document appear in a portrait orientation was ignored. Instead, the document appeared in a landscape

问题 Problem I am working with data on a logarithmic scale and would like to rotate it to fit a line. I know the model but am unsure quite what angle I should be plugging into transform_angles to recover the correct rotation. After a bit of trial and error I know the answer is around 10 degrees for the axes limits I require. MWE import matplotlib.pylab as plt import numpy as np plt.clf() plt.yscale('log') plt.ylim((1e-11, 1e-1)) # Other data is usually plotted and these are the ranges I need. plt

问题 In a navigation-based app, LandscapeViewController only supports landscape mode (all others support both modes). I also have a "loading screen" that advises the user to rotate the phone before continuing. This way I can make sure that when my landscape view loads, that it's in landscape mode. The problem comes when I rotate the phone to portrait mode while still showing LandscapeVC. I press the Back navigation button to navigate up one level (to a VC that supports both landscape and portrait