# Instance rotation? **URL:** \ **Category:** CesiumJS\ **Created:** [July 8, 2020, 1:50pm UTC](https://community.cesium.com/t/instance-rotation/10163 "2020-07-08T13:50:53Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![bertt](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/bertt/32/2702_2.png) [@bertt](https://community.cesium.com/u/bertt)\ **Post date:** [July 8, 2020, 1:50pm UTC](https://community.cesium.com/t/instance-rotation/10163/1 "2020-07-08T13:50:53Z")
I’m experimenting with adding instance rotation in i3dm tiles, but it’s unclear to me how it works. In [https://bertt.github.io/cesium\_3dtiles\_samples/samples/instanced/index\_north.html](https://bertt.github.io/cesium_3dtiles_samples/samples/instanced/index_north.html) I’ve added 1 i3dm tile (seat\_north.i3dm) with 1 instance (a seat, ecef location 1214947.2, -4736379, 4081540.8) pointing to the north and no NORMAL\_UP and NORMAL\_RIGHT defined. I’m using EAST\_NORTH\_UP = true otherwise the seat is wrongly rotated. Result looks ok. ![no_normals](https://global.discourse-cdn.com/cesium/original/2X/f/f28207aa8ace1fe5429aac1a76a736c699f9463d.png) Now I want to rotate the seat horizontally pointing eastwards. As a first test I’ve added NORMAL\_UP (0, 1, 0) and NORMAL\_RIGHT (1, 0, 0) to the i3dm tile (seat\_east.i3dm). Now the seat is rotated strangely, I was expecting the same result as the seat pointing north (because no rotation with these normals). Result see [https://bertt.github.io/cesium\_3dtiles\_samples/samples/instanced/index\_east.html](https://bertt.github.io/cesium_3dtiles_samples/samples/instanced/index_east.html) ![rotated](https://global.discourse-cdn.com/cesium/original/2X/6/6da64e1f31a872c161bfbff0e884511358765143.png) So my question is: How do I calculate the NORMAL\_UP and NORMAL\_RIGHT vector so the seat is rotating horizontally to the east? Bonusquestion: Why is the color of the seat different everytime I load Cesium?? ---
**Author:** ![Hyper\_Sonic](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/hyper_sonic/32/2255_2.png) [@Hyper\_Sonic](https://community.cesium.com/u/Hyper_Sonic)\ **Post date:** [July 8, 2020, 3:33pm UTC](https://community.cesium.com/t/instance-rotation/10163/2 "2020-07-08T15:33:25Z")
Chair facing north I assume the seat normals would be (in respects to the local ENU frame) normal\_dir: (0,1,0) pointing north normal\_right: (1,0,0) pointing east normal\_up: (0,0,1) pointing up Chair facing east should be: normal\_dir: (1,0,0) pointing east normal\_right: (0,-1,0) pointing south normal\_up: (0,0,1) pointing up (unchanged) If needed these vectors could be transformed to the global Earth frame. The way you set it probably had the chair’s front lying on the ground NORMAL\_UP (0, 1, 0) up pointing north NORMAL\_RIGHT (1, 0, 0) right pointing east ---
**Author:** ![bertt](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/bertt/32/2702_2.png) [@bertt](https://community.cesium.com/u/bertt)\ **Post date:** [July 8, 2020, 3:52pm UTC](https://community.cesium.com/t/instance-rotation/10163/3 "2020-07-08T15:52:51Z")
Hi, ok thanks, if I use your suggestion it does not rotate well: normal\_right: (0,-1,0) pointing south normal\_up: (0,0,1) pointing up (unchanged) ![seat](https://global.discourse-cdn.com/cesium/original/3X/0/f/0f472879387d1b15a44f58a16417f8fffab6374b.png) “If needed these vectors could be transformed to the global Earth frame.” Interesting, how can I do that? Do i need to provide the normal\_right and normal\_up in i3dm in local or global earth frame? ---
**Author:** ![Hyper\_Sonic](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/hyper_sonic/32/2255_2.png) [@Hyper\_Sonic](https://community.cesium.com/u/Hyper_Sonic)\ **Post date:** [July 9, 2020, 2:27am UTC](https://community.cesium.com/t/instance-rotation/10163/4 "2020-07-09T02:27:00Z")
This is a bit long, I’m sure there’s a Cesium matrix function that can do these rotation transforms, just not sure which function name as I’ve been using my math library lately. So trying it ‘long hand’ by just using Cartesian3 math. This is untested code, so let me know if it works. EDIT: what was I thinking, Cesium Cartesian3s are not stored in arrays like matrices, rather objects with x,y,z properties…Ignore this code, updated code posted later on this thread. ```auto //get ENU vectors in terms of Earth Fixed GD_transform = Cesium.Transforms.eastNorthUpToFixedFrame(position, viewer.scene.globe.ellipsoid, new Cesium.Matrix4()); GD_E=new Cesium.Cartesian3(GD_transform[0],GD_transform[1],GD_transform[2]); GD_N=new Cesium.Cartesian3(GD_transform[4],GD_transform[5],GD_transform[6]); GD_U=new Cesium.Cartesian3(GD_transform[8],GD_transform[9],GD_transform[10]); //get chair vectors in terms of ENU frame lNorth = new Cesium.Cartesian3(1,0,0); lEast = new Cesium.Cartesian3(0,-1,0); //vector declarations let c1=[];var c2=[];let c3=[];let temp=[]; let EFnorth=[]; let EFeast=[]; //get EFnorth from lNorth Cesium.Cartesian3.multiplyByScalar(GD_E, lNorth.x, c1); Cesium.Cartesian3.multiplyByScalar(GD_N, lNorth.y, c2); Cesium.Cartesian3.multiplyByScalar(GD_U, lNorth.z, c3); Cesium.Cartesian3.add(c1, c2, temp); //c1+c2 result to temp Cesium.Cartesian3.add(temp, c3, EFnorth); //temp+c3 result to EFnorth //get EFeast from lEast Cesium.Cartesian3.multiplyByScalar(GD_E, lEast.x, c1); Cesium.Cartesian3.multiplyByScalar(GD_N, lEast.y, c2); Cesium.Cartesian3.multiplyByScalar(GD_U, lEast.z, c3); Cesium.Cartesian3.add(c1, c2, temp); //c1+c2 result to temp Cesium.Cartesian3.add(temp, c3, EFeast); //temp+c3 result to EFnorth //get EFup (the chair is upright) let EFup=GD_U; ``` EDIT: Actually since you already know EFup, just find either EFnorth or EFeast, then use cross to find the 3rd Cesium.Cartesian3.cross(left, right, result) ---
**Author:** ![bertt](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/bertt/32/2702_2.png) [@bertt](https://community.cesium.com/u/bertt)\ **Post date:** [July 9, 2020, 4:01pm UTC](https://community.cesium.com/t/instance-rotation/10163/5 "2020-07-09T16:01:10Z")
I’ve tried your code with position = new Cesium.Cartesian3(1214947.2, -4736379, 4081540.8). Result: EFup: x: 0.19022214020877842, y: -0.7415665061164088, z: 0.6433464497303876 EFeast: x: 0.1598520208967612, y: -0.6231709121869502, z: -0.765575173068789 When using these values in the i3dm for NORMAL\_UP and NORMAL\_RIGHT (is this ok?), it looks like the chair is fallen on the back ☹ ![back](https://global.discourse-cdn.com/cesium/original/2X/b/bad3dc56ddb2938e3d2b8a4a4a490b82299233f1.png) Looks like we’re getting close with this… Note: the actual usecase is rotating horizontally to an angle (angle between 0 and 360, 0 == north), so not just rotating east. ---
**Author:** ![Hyper\_Sonic](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/hyper_sonic/32/2255_2.png) [@Hyper\_Sonic](https://community.cesium.com/u/Hyper_Sonic)\ **Post date:** [July 9, 2020, 5:48pm UTC](https://community.cesium.com/t/instance-rotation/10163/6 "2020-07-09T17:48:22Z")
Perhaps the model’s up vector is not through the back support but rather through the seat. If that’s the case maybe try: lEast = new Cesium.Cartesian3(0,a,b); //unknown, but make sure it’s orthogonal to the other 2 lNorth = new Cesium.Cartesian3(0,a,b); //unknown, but make sure it’s orthogonal to the other 2 lUp = new Cesium.Cartesian3(1,0,0); //model’s up vector facing east some combinations to try for a and b (some of these might break the right hand rule) a=1;b=0; a=0;b=1; a=-1;b=0; a=0;b=-1; I made a transform function to save code lines. Earlier I mistakenly declared Cartesian3 as arrays, when they actually have xyz object properties, I suppose you already made the correction? I altered the code accordingly ```auto function vectorTransform(lv, tm, ov) { //lv local vector, tm transform matrix, ov output vector let GD_E=new Cesium.Cartesian3(tm[0],tm[1],tm[2]); let GD_N=new Cesium.Cartesian3(tm[4],tm[5],tm[6]); let GD_U=new Cesium.Cartesian3(tm[8],tm[9],tm[10]); let c1= new Cesium.Cartesian3();let c2= new Cesium.Cartesian3(); let c3= new Cesium.Cartesian3();let temp= new Cesium.Cartesian3(); Cesium.Cartesian3.multiplyByScalar(GD_E, lv.x, c1); Cesium.Cartesian3.multiplyByScalar(GD_N, lv.y, c2); Cesium.Cartesian3.multiplyByScalar(GD_U, lv.z, c3); Cesium.Cartesian3.add(c1, c2, temp); //c1+c2 result to temp Cesium.Cartesian3.add(temp, c3, ov); //temp+c3 result to ov } //vector declarations let EFnorth= new Cesium.Cartesian3(); let EFeast= new Cesium.Cartesian3(); let EFup= new Cesium.Cartesian3(); //local vectors (un-comment the combo to try) y1=1; z1=0; y2=0; z2=1; //y1=0 ;z1=-1; y2=-1; z2=0; //y1=-1 ;z1=0; y2=0; z2=-1; //y1=0 ;z1=1; y2=1; z2=0; let lEast = new Cesium.Cartesian3(0,y1,z1); //unknown, but make sure it's orthogonal to the other 2 let lNorth = new Cesium.Cartesian3(0,y2,z2); //unknown, but make sure it's orthogonal to the other 2 let lUp = new Cesium.Cartesian3(1,0,0); //model's up vector facing east /* old code segment (what was I thinking) a=1;b=0; //a=0;b=1; //a=-1;b=0; //a=0;b=-1; let lEast = new Cesium.Cartesian3(0,a,b); //unknown, but make sure it's orthogonal to the other 2 let lNorth = new Cesium.Cartesian3(0,a,b); //unknown, but make sure it's orthogonal to the other 2 let lUp = new Cesium.Cartesian3(1,0,0); //model's up vector facing east */ GD_transform = Cesium.Transforms.eastNorthUpToFixedFrame(position, viewer.scene.globe.ellipsoid, new Cesium.Matrix4()); vectorTransform(lEast,GD_transform,EFeast); vectorTransform(lNorth,GD_transform,EFnorth); vectorTransform(lUp,GD_transform,EFUp); ``` ---
**Author:** ![bertt](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/bertt/32/2702_2.png) [@bertt](https://community.cesium.com/u/bertt)\ **Post date:** [July 9, 2020, 6:44pm UTC](https://community.cesium.com/t/instance-rotation/10163/7 "2020-07-09T18:44:50Z")
In Blender the seat.glb looks like: ![blender](https://global.discourse-cdn.com/cesium/original/2X/5/553a198ab9e135b86227d06a87a62c0f5155a11f.png) ---
**Author:** ![bertt](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/bertt/32/2702_2.png) [@bertt](https://community.cesium.com/u/bertt)\ **Post date:** [July 9, 2020, 7:09pm UTC](https://community.cesium.com/t/instance-rotation/10163/8 "2020-07-09T19:09:28Z")
I’ve tried your last code with position = new Cesium.Cartesian3(1214947.2, -4736379, 4081540.8), the third option (a=-1;b=0) gives good result 🙂 ![yeah](https://global.discourse-cdn.com/cesium/original/2X/a/a8a2d333461a997918b59f4c1c09e3276ad343ce.png) normals used: normal\_up (from EFup): {x: 0.9686397001928082, y: 0.24846957803801, z: 0} normal\_right (from EFeast): {x: 0.1598520208967612, y: -0.6231709121869502, z: -0.765575173068789} Thanks for your help! Next week I’ll try to get all the rotations (seat angles between 0-360) working well. ---
**Author:** ![Hyper\_Sonic](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/hyper_sonic/32/2255_2.png) [@Hyper\_Sonic](https://community.cesium.com/u/Hyper_Sonic)\ **Post date:** [July 9, 2020, 8:05pm UTC](https://community.cesium.com/t/instance-rotation/10163/9 "2020-07-09T20:05:17Z")
Looks like you’ve caught another error of mine. Instead of a,b I meant something like this (updated the above code already): (0,y1,z1) (0,y2,z2) (1,0,0) with combos like y1=1; z1=0; y2=0; z2=1; y1=0 ;z1=-1; y2=-1; z2=0; y1=-1 ;z1=0; y2=0; z2=-1; y1=0 ;z1=1; y2=1; z2=0; With a=-1 b=0 that would mean let lEast = new Cesium.Cartesian3(0,-1,0); let lNorth = new Cesium.Cartesian3(0,-1,0); Which have should have failed as they are not orthogonal, unless you just used one of them in which case it should be fine. Did you just use the east or north by chance? I’m wondering if the backrest is the right or forward vector, as it would appear that the up vector is the seat (Blender y to Cesium up) I’m glad that it is working! Can rotate vectors about other vectors to get non-cardinal rotations. ---
**Author:** ![bertt](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/bertt/32/2702_2.png) [@bertt](https://community.cesium.com/u/bertt)\ **Post date:** [July 10, 2020, 6:57am UTC](https://community.cesium.com/t/instance-rotation/10163/10 "2020-07-10T06:57:24Z")
yes in the working version I used only EFup (for normal\_up in i3dm tile) and EFeast (for normal\_right in i3dm tile) and not EFnorth. I suppose EFup and EFeast are orthogonal. > [@bertt](#): > > normal\_up (from EFup): {x: 0.9686397001928082, y: 0.24846957803801, z: 0} > normal\_right (from EFeast): {x: 0.1598520208967612, y: -0.6231709121869502, z: -0.765575173068789} ---
**Author:** ![Hyper\_Sonic](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/hyper_sonic/32/2255_2.png) [@Hyper\_Sonic](https://community.cesium.com/u/Hyper_Sonic)\ **Post date:** [July 10, 2020, 3:31pm UTC](https://community.cesium.com/t/instance-rotation/10163/11 "2020-07-10T15:31:59Z")
Ah OK. If orthogonal their dot product would be zero (or very close to) which they are. So for an upright chair facing east: lEast (0,-1,0) right side of chair facing south lUp (1,0,0) seat of chair facing east then this should be the case: lNorth (0,0,-1) chair legs facing down I assume you’d want to rotate it around it’s vertical axis (LNorth in this case.) This should be doable just by using sin and cos. ```auto let deg=0; //in degrees (east is 0 degrees, range: -180 to +180) let rad=deg*Math.PI/180; //radians let lUp=(Math.Cos(rad),Math.Sin(rad),0); let lEast=(Math.Cos(rad-Math.PI/2),Math.Sin(rad-Math.PI/2),0); ``` then convert local to global ---
**Author:** ![bertt](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/bertt/32/2702_2.png) [@bertt](https://community.cesium.com/u/bertt)\ **Post date:** [July 14, 2020, 2:14pm UTC](https://community.cesium.com/t/instance-rotation/10163/12 "2020-07-14T14:14:02Z")
FYI: got it working now for seats in a stadium (note with random seats subset) 🙂 ![stadium](https://global.discourse-cdn.com/cesium/original/2X/2/285299d03d0bfaa9431c4475abb2a66be5eabdd7.jpeg) ---
**Author:** ![Hyper\_Sonic](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/hyper_sonic/32/2255_2.png) [@Hyper\_Sonic](https://community.cesium.com/u/Hyper_Sonic)\ **Post date:** [July 14, 2020, 4:59pm UTC](https://community.cesium.com/t/instance-rotation/10163/13 "2020-07-14T16:59:24Z")
Awesome! Can set the direction of the seats as well? They seem to all be facing roughly the same direction in the image. ---
**Author:** ![bertt](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/bertt/32/2702_2.png) [@bertt](https://community.cesium.com/u/bertt)\ **Post date:** [July 14, 2020, 5:51pm UTC](https://community.cesium.com/t/instance-rotation/10163/14 "2020-07-14T17:51:45Z")
yes they are all rotated to an angle (seat facing the field) ---
**Author:** ![bertt](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/bertt/32/2702_2.png) [@bertt](https://community.cesium.com/u/bertt)\ **Post date:** [July 21, 2020, 8:02pm UTC](https://community.cesium.com/t/instance-rotation/10163/15 "2020-07-21T20:02:48Z")
Hi @Hyper_Sonic , a related question: this time I want to rotate a b3dm model (lets say facing east again), I think I have to change the transform values in tileset.json. At the moment I only use the GD\_transform values in the transform to place the model correctly. Should I compute normal\_up and normal\_right again to rotate the model? How do I put it in the transform? ---
**Author:** ![Hyper\_Sonic](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/hyper_sonic/32/2255_2.png) [@Hyper\_Sonic](https://community.cesium.com/u/Hyper_Sonic)\ **Post date:** [July 21, 2020, 9:23pm UTC](https://community.cesium.com/t/instance-rotation/10163/16 "2020-07-21T21:23:47Z")
I think I’d need more information. The only json file I see is the one referenced in your link at the top of the thread [bertt.github.io/cesium\_3dtiles\_samples/samples/instanced/tileset\_north.json](http://bertt.github.io/cesium_3dtiles_samples/samples/instanced/tileset_north.json) The only thing there that looked remotely like vectors was region, but I discovered it was not: [https://docs.opengeospatial.org/cs/18-053r2/18-053r2.html#32](https://docs.opengeospatial.org/cs/18-053r2/18-053r2.html#32) [west, south, east, north, minimum height, maximum height] So the first 4 are lon/lat values in radians, and the last 2 are heights in meters. Without further data, I’d say just try simple local orientation vectors again then transform to the local ENU transform and see what it takes to orient upright facing east again. ---
**Author:** ![bertt](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/bertt/32/2702_2.png) [@bertt](https://community.cesium.com/u/bertt)\ **Post date:** [July 21, 2020, 9:35pm UTC](https://community.cesium.com/t/instance-rotation/10163/17 "2020-07-21T21:35:10Z")
ah yes, I’m trying to rotate the building.b3dm model in [https://bertt.github.io/cesium\_3dtiles\_samples/samples/b3dm/index.html](https://bertt.github.io/cesium_3dtiles_samples/samples/b3dm/index.html) tileset.json: [https://bertt.github.io/cesium\_3dtiles\_samples/samples/b3dm/tileset.json](https://bertt.github.io/cesium_3dtiles_samples/samples/b3dm/tileset.json) If I modify the boundingVolume.box elements, only the white debug boxes are moved/rotated, but not the model ☹ So I think I need to change the transform array somehow. The transform now contains GD\_transform of lon=-75.61 lat = 40.04 . As alternative I’m considering to rotate the glTF model before putting it in the b3dm, but I hope there is a better way… ---
**Author:** ![Hyper\_Sonic](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/hyper_sonic/32/2255_2.png) [@Hyper\_Sonic](https://community.cesium.com/u/Hyper_Sonic)\ **Post date:** [July 21, 2020, 11:06pm UTC](https://community.cesium.com/t/instance-rotation/10163/18 "2020-07-21T23:06:12Z")
I’ve tried messing with it using the console, but I can’t seem alter rotations though. I typed this into the console ```auto var cr=viewer.scene.camera.right; var cd=viewer.scene.camera.direction; var cu=viewer.scene.camera.up; var cp=viewer.scene.camera.position; ``` I then tried both of the following with to no avail (move house to camera) ```auto tileset.modelMatrix={0: cr.x, 1: cr.y, 2: cr.z, 3: 0, 4: cd.x, 5: cd.y, 6: cd.z, 7: 0, 8: cu.x, 9: cu.y, 10: cu.z, 11: 0, 12: cp.x, 13: cp.y, 14: cp.z, 15: 1}; tileset._modelMatrix={0: cr.x, 1: cr.y, 2: cr.z, 3: 0, 4: cd.x, 5: cd.y, 6: cd.z, 7: 0, 8: cu.x, 9: cu.y, 10: cu.z, 11: 0, 12: cp.x, 13: cp.y, 14: cp.z, 15: 1}; ``` Odd thing is you can move it around a bit, this moves it up a bit: ```auto tileset.modelMatrix={0: 1, 1: 0, 2: 0, 3: 0, 4: 0, 5: 1, 6: 0, 7: 0, 8: 0, 9: 0, 10: 1, 11: 0, 12: 0, 13: 0, 14: 20, 15: 1}; ``` Then this moves it up and right a bit: ```auto tileset.modelMatrix={0: 1, 1: 0, 2: 0, 3: 0, 4: 0, 5: 1, 6: 0, 7: 0, 8: 0, 9: 0, 10: 1, 11: 0, 12: 40, 13: 0, 14: 20, 15: 1}; ``` I’ve tried different rotations, but the house wouldn’t appear ```auto //rotate 90deg CW around z tileset.modelMatrix={0: 0, 1: -1, 2: 0, 3: 0, 4: 1, 5: 0, 6: 0, 7: 0, 8: 0, 9: 0, 10: 1, 11: 0, 12: 0, 13: 0, 14: 0, 15: 1}; //rotate 90deg CCW around z tileset.modelMatrix={0: 0, 1: 1, 2: 0, 3: 0, 4: -1, 5: 0, 6: 0, 7: 0, 8: 0, 9: 0, 10: 1, 11: 0, 12: 0, 13: 0, 14: 20, 15: 1}; ``` That transform in the JSON is entered to \_clippingPlanesOriginMatrix Not sure if that’s causing the house to disappear on rotations. I’ve even tried ```auto tileset.root.children[0]._tileset.modelMatrix={0: cr.x, 1: cr.y, 2: cr.z, 3: 0, 4: cd.x, 5: cd.y, 6: cd.z, 7: 0, 8: cu.x, 9: cu.y, 10: cu.z, 11: 0, 12: cp.x, 13: cp.y, 14: cp.z, 15: 1}; tileset.root.children[0]._tileset._modelMatrix={0: cr.x, 1: cr.y, 2: cr.z, 3: 0, 4: cd.x, 5: cd.y, 6: cd.z, 7: 0, 8: cu.x, 9: cu.y, 10: cu.z, 11: 0, 12: cp.x, 13: cp.y, 14: cp.z, 15: 1}; ``` ---
**Author:** ![Hyper\_Sonic](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/hyper_sonic/32/2255_2.png) [@Hyper\_Sonic](https://community.cesium.com/u/Hyper_Sonic)\ **Post date:** [July 21, 2020, 11:30pm UTC](https://community.cesium.com/t/instance-rotation/10163/19 "2020-07-21T23:30:47Z")
That transform in the JSON file. I believe that is the local ENU transform for that location. Yes, it is, If I place the camera near the house and type this in the console (EDIT: reading back on your previous post I should have known!) ```auto Cesium.Transforms.eastNorthUpToFixedFrame(viewer.scene.camera.position, viewer.scene.globe.ellipsoid, new Cesium.Matrix4()); ``` I get that transform. So the modelMatrix position apparently is transformed by that transform. Hmm, now how to rotate it. My rotation attempts should have worked, where I tried to rotate 90deg in either direction. Those new rotation vectors should have been transformed just like the position vector was. In any event you should see the house, even if at a funny orientation. Try replacing the transform in the json with this. I took the one that’s there now and rotated it 90deg around it’s up vector. Possibly it’ll rotate the house 90deg, who knows. (corrected, first time I rotated 90 radians!) ```auto [ 0.5719022525624771, 0.6163388209036162, 0.541344904867667, 0, -0.7979626193589172, 0.2649554064190438, 0.5413449162659866, 0, 0.19021961055045852, -0.7415693387513873, 0.6433439241941505, 0, 1214931, -4736397, 4081525, 1 ] ``` ---
**Author:** ![bertt](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/bertt/32/2702_2.png) [@bertt](https://community.cesium.com/u/bertt)\ **Post date:** [July 22, 2020, 8:12am UTC](https://community.cesium.com/t/instance-rotation/10163/20 "2020-07-22T08:12:48Z")
Ok thanks, I see the house rotating indeed 🙂 > [@Hyper\_Sonic](#): > > I took the one that’s there now and rotated it 90deg around it’s up vector. What formula did you use for this? For the up vector I’ve calculated: (lon, lat, alt) = -75.6132, 40.0416, 0 ecef = 1214931, -4736397, 4081525 transform = 0.9686, 0.2484, 0, 0, -0.1598, 0.6231, 0.765,0,0.1902, -0.7415, 0.6433, 0, 1214931, -4736397, 4081525, 1 east = 0.9686, 0.2484, 0 up = -0.1598, 0.6231, 0.7655 [Next page](https://community.cesium.com/t/instance-rotation/10163.md?page=2)