Perspective

[tonylondon]

Can anyone help me with persective? The attached gif shows a chequered floor and I have attempted to show it in the horizontal position. Unfortunately, the perspective envelope I used does not take account of forshortening and I have had to guess. Does anyone know how much forshortening I should apply in relation to any of the other dimensions, in order for the tiles to appear square?
Thanks
Tony

[tonylondon]

Can anyone help me with persective? The attached gif shows a chequered floor and I have attempted to show it in the horizontal position. Unfortunately, the perspective envelope I used does not take account of forshortening and I have had to guess. Does anyone know how much forshortening I should apply in relation to any of the other dimensions, in order for the tiles to appear square?
Thanks
Tony

[gwpriester]

Tony

I did a little researching in Google.

Java Sketchpad Is a real time perspective cube which you can adjust in perspective. Doesn't answer your question but it is worth a look.

Plotting a Perfect Square in 1-Point Perspective appears to have more information on the topic.

Drawing Grids in 1-Point Perspective is a continuation of the previous article and hits the nail right on the head :-)

Gary

Gary Priester

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[Luciano]

Don't forget the importance of the relative position of the observer and the object.
You will need to resize your object before applying Xara perspective tool.
I hope the attached image I prepared in Xara will be helpful.

Ciao

Luciano

[Luciano]

I followed Gary suggestion of searching links with Google.
I used as keywords: perspective horizon plane.
One link I found was very interesting:http://www.webdeveloper.com/design/d...pective_2.html

Luciano

[Clements]

Luciano and Gary, thank you!

If an artist (or group of artists) is willing to volunteer, I sure would like to see a series of hints/tips-n-tricks of BASIC DRAWING TECHNIQUES. Of course, how to integrate Xara's tools would be necessary part of the instruction.

I believe that aspects of perspective drawing would be a good place to start. Luciano's example would be an excellent kick-off point.

I kind of tried to make a stab at this with the isometric mini-tutorial. (Looking back, a series of smaller tuts may have been more effective.)

How do others feel? Is this forum a practical way of doing this? Are there any of you talented folks who have a particular passion you'd like to share which could help forum members who are less talented?

It could be quite rewarding, but may also require the investment of time and effort.

Other courses could involve: Lighting (how to use gradients, etc. to show volume and shadows), Texturing (how to simulate surface textures and surface inconsistencies), Color Composition, effective graphical representation of data (graphs, diagrams), Charts, Portraiture, Cartooning, etc.

[tonylondon]

Well, Luciano,
Thank you for your very clear diagrams. It seems I didn't consider the distance of the observer from the picture. If I assume my screen to be my picture my face is about 1.5 x screen height away. If I simplify your diagram by assuming my tile is at the bottom of the screen, then using the process of similar triangles I estimate a forshortening to 25% of the original. This seems to give reasonable results. The diagram below is not to scale.
Than k you both Luciano and Gary for your references. Coincidentally it was in the design of a perspective cage that I first met my problem, so the article on the grid will be especially relevant. I can see it is going to take me quite a while to analyse the articles get to grips with perspective. I am sure I shall need to get back to this thread again.
Tony

[tonylondon]

Here are the first results of my investigations
Perspective Tunnel
To change vanishing point:
One thing I have learnt is that there isn't just one vanishing point, rather one for each orientation of the object you are creating. It also varies with the desired position of the horizon. My grid has the centre of the screen as the starting point, with a viewing distance that is comfortable for me. I can post a zipped copy if anyone is interested (on past experience, probably not!)
Move the large cross to where you want the vanishing point to appear. Select page frame and large vanishing point (available from the name gallery), klone and group and reduce to 13% with aspect ratio locked.Zoom in and move the group until the large and small crosses coincide. This is the tunnel end. Select each grid in turn and drag the closest side until it lines up exactly with the edge of the tunnel end. Select the mould tool and the vanishing point appears. Reset it to the new position indicated by the cross. After fine tuning of all four grids zoom out to the desired normal view.
To change viewing distance:
If the rectangles do not look square you will need to modify the tunnel for viewing distance. A more distant viewing distance will require more forshortening (I think). For small adjustments expand or contract the tunnel end and realign the grid faces as above. For larger changes, change the number of grid markers. These are created in my case with the blend tool and can be adjusted by setting a new step number.
Adding more grids:
It is a good idea to use additional layers which can be rendered invisible when not required. Copy the closest grid and move it so that the front edge is where it is needed. It will be so many grid markers from the edge. Drag the back of the new grid to the equivalent position at the back of the tunnel. Then select the mould tool and move its vanishing point to line up with the others.
To use:
Create your object and place on a temporary square background and group. Move so that the desired front edge lines up with the appropriate grid and is at that point the correct size. Drag the opposite edge to the desired location (the image will forshorten) then select the mould tool and the appropriate perspective envelope. Drag the objects vanishing point to line up with the picture's vanishing point indicated by the large cross. Finally ungroup and remove temporary square.
Does all this make sense?
Tony

[arnold foss]

I would like to see the zipped file for this. You can e-mail it to me if you like.

Thank-you
Arnold