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Top: Autodesk Maya: Scripts : How to sample color at any given point in a ramp

From our website www tjgalda com Skill level intermediate How do you query the colour in a ramp at any given point Frustratingly this isnt quite as simple as it sounds Even the technical documentation from Autodesk states Currently the routines to get the value of a ramp structure with interpolation are not available through MEL which limits the use of this control by end users So we have to work around it in this case We are able to sample the ramp and get back i how many colour entries there are ii where they are in the ramp and iii what colour they are From that data we can approximate fairly well what the ramp looks like Lets build the tool for our example to do so on a relatively simple scale You can add complexity later but to keep things simple were going to sample a simple ramp with two colours and a linear interpolation between the two colours A ramp such as this mel code will create Note you can view all the mel on the website www tjgalda com Create the gradient using a ramp string tempName shadingNode asShader ramp string tj rampNode rename tempName tj gradientColour string tj rampWin window t tj Ramp Viewer tj rampWin columnLayout rampColorPort node tj rampNode showWindow tj rampWin setAttr tj rampNode colorEntryList 0 color type double3 0 988 1 0 8 setAttr tj rampNode colorEntryList 1 color type double3 0 0 0 235 setAttr tj rampNode colorEntryList 1 position 1 0 removeMultiInstance break true tj rampNode colorEntryList 2 showWindow tj rampWin Now that we have the ramp we can gather information about the ramp We need to determine where are they and what colour create an array to catch each position and match the entry in the list of the ramp Finally we will create an array to catch colour use a vector array to maintain match in the list of the ramp Where are they and what colour Create an array to catch each position and match entry in list int entries getAttr size tj rampNode colorEntryList vector entry colour for i 0 i entries i entry pos i getAttr tj rampNode colorEntryList i position float entryList colours getAttr tj rampNode colorEntryList i color entry colour i and print back the results print n entry pos is n n print entry pos print nn n entry colour is n n print entry colour entry pos is 0 1 entry colour is 0 988 1 0 8 0 0 0 235 In our example now we can see that we have the two colour entries at 0 and 1 with the associated colour mix Now we can work with some basic calculations to deduce what the colours are between After we know the colour information we can then begin to deduce what the ramp is like The first step is to find the difference or delta between the two colours on each channel From there we can divide up the colour on regular intervals and determine what the exact colour is at any specific point on the map This is a sampling step How many intervals should we break the ramp into int step 20 Find the delta difference for each channel Use temp vectors to get data out of the array easily For our example to keep it simple we can make some assumptions about where each entry is and what colours they are We will assume only two colours and that the first colour is brighter Of course one should build in robustness to remove these assumptions with true data vector tempTopV entry colour 0 vector tempBotV entry colour 1 Use absolute to ensure its not a negative value float differenceR abs tempTopV x tempBotV x float differenceG abs tempTopV y tempBotV y float differenceB abs tempTopV z tempBotV z Divide up the delta per step This is the amount of change per step that each colour travels float deltaStepR differenceR step float deltaStepG differenceG step float deltaStepB differenceB step Now start number delta per step the number of steps end number in other words we have broken down what the difference can be at each interval Finalize by building the arrays float colourStepsR colourStepsG colourStepsB colourStepsR 0 tempBotV x colourStepsG 0 tempBotV y colourStepsB 0 tempBotV z Each new step is the old step the delta for that colour for i 1 i

How to sample color at any given point in a ramp

From our website: www.tjgalda.com Skill level: intermediate How do you query the colour in a ramp at any given point? Frustratingly, this isnt quite as simple as it sounds. Even the technical documentation from Autodesk states: Currently the routines to get the value of a ramp structure (with interpolation) are not available through MEL, which limits the use of this control by end users. So, we have to work around it in this case. We are able to sample the ramp and get back i)how many colour entries there are, ii)where they are in the ramp and iii) what colour they are. From that data, we can approximate fairly well what the ramp looks like. Lets build the tool for our example to do so on a relatively simple scale. You can add complexity later, but to keep things simple, were going to sample a simple ramp with two colours and a linear interpolation between the two colours. A ramp such as this mel code will create: Note: you can view all the mel on the website. www.tjgalda.com Create the gradient using a ramp: string $tempName = `shadingNode -asShader ramp`; string $tj_rampNode = `rename $tempName tj_gradientColour`; string $tj_rampWin = `window -t tj Ramp Viewer tj_rampWin`; columnLayout; rampColorPort -node $tj_rampNode; showWindow $tj_rampWin; setAttr ($tj_rampNode + .colorEntryList[0].color) -type double3 0.988 1 0.8 ; setAttr ($tj_rampNode + .colorEntryList[1].color) -type double3 0 0 0.235 ; setAttr ($tj_rampNode + .colorEntryList[1].position) 1.0; removeMultiInstance -break true ($tj_rampNode + .colorEntryList[2]); showWindow $tj_rampWin; Now that we have the ramp, we can gather information about the ramp. We need to determine where are they and what colour, create an array to catch each position and match the entry in the list of the ramp. Finally we will create an array to catch colour, use a vector array to maintain match in the list of the ramp. Where are they and what colour? Create an array to catch each position and match entry in list. int $entries = `getAttr -size ($tj_rampNode+.colorEntryList)`; vector $entry_colour[]; for ($i = 0; $i < $entries; $i ++) { $entry_pos[$i] = `getAttr ($tj_rampNode+.colorEntryList[+$i+].position)`; float $entryList_colours[] = `getAttr ($tj_rampNode+.colorEntryList[+$i+].color)`; $entry_colour[$i] = >; } //and print back the results print ("n$entry_pos[] is n==================n"); print $entry_pos; print ("nn==================n$entry_colour[] is n==================n); print $entry_colour; $entry_pos[] is ================== 0 1 ================== $entry_colour[] is ================== 0.988 1 0.8 0 0 0.235 In our example now, we can see that we have the two colour entries at 0 and 1, with the associated colour mix. Now we can work with some basic calculations to deduce what the colours are between. After we know the colour information, we can then begin to deduce what the ramp is like. The first step is to find the difference or delta between the two colours on each channel. From there, we can divide up the colour on regular intervals and determine what the exact colour is at any specific point on the map. This is a sampling step. How many intervals should we break the ramp into? int $step = 20; Find the delta/difference for each channel. Use temp vectors to get data out of the array easily. For our example to keep it simple, we can make some assumptions about where each entry is and what colours they are. We will assume only two colours, and that the first colour is brighter. Of course, one should build in robustness to remove these assumptions with true data. vector $tempTopV = $entry_colour[0]; vector $tempBotV = $entry_colour[1]; Use absolute to ensure its not a negative value float $differenceR = `abs($tempTopV.x - $tempBotV.x)`; float $differenceG = `abs($tempTopV.y - $tempBotV.y)`; float $differenceB = `abs($tempTopV.z - $tempBotV.z)`; Divide up the delta per step. This is the amount of change per step that each colour travels. float $deltaStepR = $differenceR / $step; float $deltaStepG = $differenceG / $step; float $deltaStepB = $differenceB / $step; Now, start number + (delta per step * the number of steps) = end number, in other words, we have broken down what the difference can be at each interval. Finalize by building the arrays. float $colourStepsR[], $colourStepsG[], $colourStepsB[]; $colourStepsR[0] = $tempBotV.x; $colourStepsG[0] = $tempBotV.y; $colourStepsB[0] = $tempBotV.z; Each new step is the old step + the delta for that colour. for ($i = 1; $i

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