Are the Mars Express Pics too Slick?

[brellis]

hey gang,<br /><br />It's been nagging me for a long time -- the Mars Express pics don't look like photos. Rather, they look like 3-D computer models. The images seem unreal to me. Does this bother anyone else? <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[qso1]

If you post a few examples or point me to them by way of a link or links, I can probably tell you if they are CGI or actual. One reason I say this is that sometimes they take image data and map it to 3D models which conform approximately to the terrain imaged. Because the probes themselves cannot approach, fly through or do study at any angle they please. 3D mapping of an object that can later be flown through etc. is sometimes done. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[brellis]

hi qso1<br /><br />Here is a 3d thing they took with the stereo camera. Look thru their gallery, it all has a slick, colorized look to me. <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[spacechump]

You have to remember that while the resolution is good on those images its is not spactacular. Also realize that multiple shots are processed to form a 3D representation of the object in question, using both camera image data and sounding data. And lastly, the colors may be considered "approximate" because colorized grayscale images were used.

 

[qso1]

I went to the link. The very first two images are 3D models that have the image data mapped to them. One of the problems in using this technique is that the light source is computer generated and the images were naturally lit. The image data is also mapped in a process called bump mapping or elevation mapping in which color information dosn't come out quite like it would on original images.<br /><br />I clicked the mars express image link where I found some 3D and some regular imagery. The regular (Lack of better term) images are normally taken with the spacecraft looking almost straight down. This makes them ideal for mapping to 3D objects. The objects themselves have to be made with accurate relief and one way to accomplish that is by mapping an image to an object with 25,000 or more polygons which are then shaped in a process known as deformation mapping. The image deforms the model in such a way as to allow it to assume with a fairly high degree of accuracy, the shape of the terrain.<br /><br />The colors of the unmapped images do look a little different than what I'm used to seeing. But gray scale and false color images are published as much or more than actual color as it would appear to human eyes.<br /><br />They are also extreme in contrast.<br /><br />The easiest way to identify mapped computer imagery is if its an oblique view, and in a few of the cases at the link. The squared shape of the model is clearly evident from the black areas which are clearly not the horizon of a round planet, even at low altitude.<br /><br />They are slicker looking than I normally expect but theyre pretty hi res as well. The closest natural looking one is the one of Pavonis Mons. The colors are pretty close but the contrast and brightness appear higher than I'm used to seeing. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[silylene old]

<font color="yellow">hey gang, <br /><br />It's been nagging me for a long time -- the Mars Express pics don't look like photos. Rather, they look like 3-D computer models. The images seem unreal to me. Does this bother anyone else? </font><br /><br />It always bothered me that the garish colorization looks like it was done by Andy Warhol, and afterwards the ESA press release never adequately distinguishes that the picture was not in "true color". We had a thread on this subject a couple of years ago, and another pre-SDC crash. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[JonClarke]

I think they are superb and can't see what you are complaining about. Are you implying they are somehow fake?<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[brellis]

<font color="yellow">I think they are superb and can't see what you are complaining about. Are you implying they are somehow fake? </font><br /><br />I'm not complaining, I'm critiquing. I'm sorry if I have hurt your feelings. Are you on the Mars Express Team?<br /><br />qso1 helped me very much with his explanation of 3D modeling. They 'colorize' the images, and there's never any atmosphere, sun, twilight, etc. This is why they don't look to this layman like photos. On the ESA site they explain how they are doing a global mapping with their stereo camera, so I understand that they are cross-referencing stereo images in the computer domain.<br /><br />Again, sorry if I hurt your feelings. <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[qso1]

brellis:<br />They 'colorize' the images, and there's never any atmosphere, sun, twilight, etc. This is why they don't look to this layman like photos.<br /><br />Me:<br />Just to clarify, the colorization is known as false color imagery at JPL. False color is the use of color that is not necessarily the natural color of the object, to heighten details in the image. The probe images are almost always looking straight down and as such, the atmosphere is usually not visible. However, clouds are sometimes present which reveal the presence of atmosphere. This type of image is not useful for the computer model because the clouds then become part of the surface detail. That is, they appear and cause bump map or deformation distortion that would not actually be present on the martian surface.<br /><br />Probes can point there cameras at the martian horizon and if so desired, get the sun in the image but I havn't seen an image with the sun in it. The optical system is probably not designed for the solar glare.<br /><br />The Viking orbiter imaged a shot of mars looking towards the horizon and like earth, a faint but visible band of atmosphere was visible. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[brellis]

You have, for lack of a better word, <i>illustrated</i> the issue for me perfectly. Thank you for that. I'm sorry I lack expertise in photography; however, as a musician, I have been a beta-tester for state-of-the-art digital samplers since I was 19 years old. <br /><br />I started out as a keyboard player/programmer on a Synclavier in 1982. It has been my job to make the sampled strings, etc from the orchestra sound as close as possible to the real deal. When the samples are too clean or 'slick' they don't sound real. I had to create sonic imperfections with dynamics and timing to make my virtual orchestra sound as real as possible. Issues of 'noise' came up often, in the context of how grainy or imperfect the sample was in the first place. Visual 'noise' is missing from the Mars Express images, and this is part of my original problem.<br /><br />Nowadays, everybody wants sampled stuff to sound gritty, cheap and edgy, so ironically I have had to unlearn everything I perfected 20 yers ago, lol.<br /><br />This is why I might be more sensitive than the average person to the 'perfectness' of the Mars Express images. They do explain what they're doing, if you read the details of their website, but not if you just click on the bbc image and story. <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[qso1]

Glad I was able to help, its usually challenging for me to come up with a description without accompanying imagery.<br /><br />No need to be sorry. I lack as much knowledge or more of how sound processing works than image processing. But one things for certain, there uses are many and varied and almost never explained by the user.<br /><br />NASA and now ESA I suppose, almost never explain some of the nuances of their publicity or publically released images.<br /><br />Years ago someone saw an image of Saturn with its moons and noticed the moons were not phased the same as Saturn, that is, not lit from the same side Saturn was. Saturn is shown IIRC at half phase while one moon was crescent, another full. The person immediatly suspected trickery. I explained that the image was simply a dramatic photo composite of images taken at different times. NASA and ESA ought to post a primer on image processing...maybe they do, but its not convieniently linked if so. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[JonClarke]

No, I am not on the MEx team (I wish!!! <img src="/images/icons/smile.gif" /> )<br /><br />The images are not colourised, they are false colour. HRSC collects data in three bands, two visible and one SWIR which are combinbed to produce a false colour image that none the less approximates what can be seen with the naked eye. many MER "colour images" use similar bands. I think the IR band is used instead of red to improve the clarity of the image, as IR has better penetration of haze. <br /><br />HRSC also collects 3-D data in the form of panchromatic stereo imagery. These are typically shown as either analgypths or converted into 3-D models which can be viewed from any angle. <br /><br />The 3-D models can also be used as a base over which other data can be draped in a GIS, for example OMEGA hyperspectral data or MOC high resolution imagery. This was done with the recent Cydonia imagery, for example.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[brellis]

hi Jon<br /><br />I wish we could change the title of this thread to "Understanding Image Processing" or something like that...<br /><br />Thanks for the detailed explanation. I've been paying much closer attention to the specs for the imagery obtained on the various interplanetary missions, so now I've got just enough info to be dangerous <img src="/images/icons/smile.gif" /><br /><br />On the Mars Images thread, rlb2 has done some great work. I especially appreciate his detailed explanations of the original image, and what processes he uses. It's an instant and ongoing education for a guy like me, someone with a "musician's eye" <img src="/images/icons/wink.gif" /><br /><br />Question: Can these rover images be interfaced with or incorporated into the stereo global-modeling images obtained by Mars Express? MRO? <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[JonClarke]

<i>Question: Can these rover images be interfaced with or incorporated into the stereo global-modeling images obtained by Mars Express? MRO?</i><br /><br />Technically yes, but the difference in scale becomes a problem. The rovers have mm pixels, the HRSC DEM has 20 m pixels. We would need intermediate steps, I suggest.<br /><br />First you create your HRSC DEM and then drape a MRO of Gusev or Meridiani over it (as has been done already using MOC images, for example at Cydonia).<br /><br />Within a portion of this you create a high resolution DEM using the rover's own stereo camera and drape the rover images over that. However you could need good coverage of rover image to do this properly<br /><br />I suspect only a few areas the rovers have visited have sufficient coverage of a large enough area to do this - parts of the Columbia Hills, Endurance crater and, hopefully. Victoria crater.<br /><br />Jon<br /> <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[vandivx]

"Nowadays, everybody wants sampled stuff to sound gritty, cheap and edgy, so ironically I have had to unlearn everything I perfected 20 yers ago, lol."<br /><br />but getting that sound 'gritty, cheap and edgy' without first knowing how to get it clean woudn't work methinks<br /><br />if we can't get realistic images as shot in the first place (same as shoooting with camera here on Earth, we have to learn how to make them from composite images and then cut down on idealistic looks of them but the point is we have to be able to obtain them as ideal and accurate as possible in the first place<br /><br />hope it makes sense <br /><br />I can think of analogy with language, if as a foreigner I wanted to talk slang English, I had to first get to know the English properly spoken and then learn to talk the slang, it never comes off well (its ridiculous) when people try to talk slang without knowing language well in the first place<br /><br />vanDivX <div class="Discussion_UserSignature"> </div>