FloatSpinner – A custom control to bypass 3dsmax value casting issues

James Haywood of Bungie Studios recently pointed out an issue on CGTalk regarding the 3ds maxscript/dotnet conversion functions. Notably it was to do with a decimal from dot net being cast into and integer in 3ds max. This could present a problem if you are using a numericupdown control in max (This is the spinner equivalent in Dot net)

James noticed that any decimal values were automatically being cast into the nearest integer. If you check the MXS help, it does indeed support this fact.

From the list, it seemed that what was needed in order for this to function in 3dsmax properly was a spinner control that returned a dotnet single as it’s event handler rather than the current decimal. This is possible. You may have read the other articles about control inheritance and custom events. The new control will be using the same principles.

Control Inheritance

It’s the one form of inheritance that the treasury isn’t thinking of taxing people on. We inherit the numericupdown control, as it already contains the functionality we need in our control, (like how we use extends in MXS). The numericupdown becomes the base class of the control.In VB you refer to this by typing MyBase. This is similar to the way you can use delegate in a scripted plugin.

Once this is done, we have to override the properties we need to change. In VB, the rough syntax for setting up a property that stores any form of information within the assembly is as follows –

private _QuantumTheory As String
<Category(“Data”), Description(“Something that nobody understands”)> _
Public Property QuantumTheory() As String
Return _QuantumTheory
End Get
Set(ByVal value As String)
_QuantumTheory = value
End Set
End Property

You’ll see that the variable is stored within a private member which is the same, except for an underscore before it. Properties are basically a function that has a get and set block. Get, in this case is called when you type something like control.QuantumTheory. It simply returns whatever is stored within the private variable _QuantumTheory. Set is called when you type something like control.QuantumTheory = “unproven”. This is the basic layout for a property the only one simpler than this is a readonly property, that do not have a set part. However, you can put whatever you like within the set part to perform error checking and options for the user. For example, you might want to check a supplied value isn’t outside the maximum or minimum range of the control, like on a spinner. Without some error checking here, you would get an exception thrown if a user tried to set this property. So you could in fact extend the to property to perform logical comparisons on the value submitted.

Another thing you can do is add information about the property. Before the property declaration, you can provide a category and description of the property. This can help organise things better, and viewing the control in Visual studio will show all categories together and provide information about the property and it’s usage. This isn’t always necessary with properties like value, and backcolor, but some properties might need clarifying. I’ll add that I’m not brilliant at doing this myself – Most of the time if I make a control, it’s just for something I’m doing so I miss this bit out if I’m in a rush. (This has been done on the XML panel download assembly though)

The properties that need to be changed are the ones that previously returned a decimal as it’s return type. You’ll see on the property declaration above that all elements are declared with the AS operator. This determines that the property returns whatever type specified. In the case of the floatspinner, here is the value property –

Shadows Property Value() As Single
Return _Value
End Get
Set(ByVal value As Single)
MyBase.Value = value
_Value = Math.Round(CSng(MyBase.Value), MyBase.DecimalPlaces)
End Set
End Property

It is declared as shadows in VB as you are using a property that exists on the base class that you want to replace. I don’t know if this is the correct or proper way to do this in VB but is the only way I have found so far. The thing to note this time is that the property returns a Single. This will mean that when this property is retrieved in 3dsmax, it will be in the correct data type for max to cast into a float, rather than the decimal to integer conversion it currently performs.

Be a DotNet Pirate – Use an Event Arrrrg

This isn’t the only thing that needs to be done. Once the properties have been overridden, the control needs to provide an event for the data to be given to 3dsmax. I have talked in the past about custom event arguments, and they are a great way to make you controls perform tasks where you get exactly the information you need out of the control, in the format ready to be used without further casting or conversion. This is recapping other posts, but is really important if you want to start to develop your own controls for max. Custom Event arguments are classes themselves, so also have properties. It is these properties that allow you to query the eventargs for the information that you want. So in the standard mouse event args, there are stored properties for that particular mouse movement that allow you to get information about the pointer –

System.Windows.Forms.MouseEventArgs Properties –

We are going to write a simple eventarg that returns a value as a single in the form of an event property. This way, we know that 3dsMax will get the correct data structure we need.

Public Class LoneRobotValueChangedEventArgs
Inherits EventArgs
Private _Value As Single
Public Property Value() As Single
Return _Value
End Get
Set(ByVal value As Single)
_Value = value
End Set
End Property
Public Sub New(ByVal Value As Single)
Me.Value = Value
End Sub
End Class

This is pretty much it, all we need to add to the custom control is the connection between the valuechanged event in the numericupdown, and our new event class. We do this by overriding that, and calling our new event class. firstly, we override the event we want to alter –

Public Shadows Event ValueChanged(ByVal sender As Object, ByVal e As LoneRobotValueChangedEventArgs)

We have changed it so that it now accepts a lonerobotValueChangedEventArgs instead of a SystemValueChangedEventArgs

Protected Overrides Sub OnValueChanged(ByVal e As System.EventArgs)
Me.Value = Math.Round(CSng(MyBase.Value), MyBase.DecimalPlaces)
RaiseEvent ValueChanged(Me, New LoneRobotValueChangedEventArgs(Math.Round(CSng(MyBase.Value), MyBase.DecimalPlaces)))
End Sub

You’ll see that when we raise the event, we do so by instantiating a new lonerobotValueChangedEventArgs object. The sender (i.e the control) is the first argument, and a second argument which is a number that is set into the event property “value”. Now that has been performs, you can retrieve this value in max as a single and therefore get the float value that you need.

Download the source for this below. As I mentioned before in the post, I haven’t had a great deal of time to write this properly, perhaps someone could add properties if needed and post the results.

download script


I also mentioned in the forum that I had seen a class in the managed services dll called maxspinner.

I couldn’t instantiate this so I asked over at the SDKblog on the Area. This was the response that I got –

Regarding your .NET Questions.

First off, a disclaimer – if a class doesn’t have specific documentation (in this class, it’s excluded) then we don’t officially support its usage.

That said, those classes are public (because they need to be used across Assembly boundaries) and we can’t really prevent anyone from at least trying. 🙂

MaxSpinner is a wrapper class that takes the Spinner custom control that we expose in Win32 and provides a managed interface so that it can be used in an interop solution. This means that we take care of instantiating the class, but the client would need to grab the handle, using MaxNativeControl::HostWindowHandle, and embed it in an interop solution (such as System.Windows.Interop.HwndHost in WPF.)

So there you are, that clears that up. MaxSpinner is not for us mortals.

Follow Up –

DotNet Supremo Yannick Peuch has managed to clear up this issue with a conversion before Max casts to and integer. Thanks for sharing this Yannick!

rollout upDownRolloutTest “NumericUpDown Control Test” width:220 height:45
dotNetControl upDownCtrl “System.Windows.Forms.NumericUpDown” pos:[10,10] width:50 height:25
dotNetControl btnGetValue “System.Windows.Forms.Button” pos:[90,10] width:100 height:21
on upDownRolloutTest open do
upDownCtrl.DecimalPlaces = 1
upDownCtrl.Increment = 0.1
upDownCtrl.Value = 1.0
upDownCtrl.Minimum = 0.0
upDownCtrl.Maximum = 10.0
btnGetValue.Text = “Get Value”
btnGetValue.FlatStyle = (dotNetClass “System.Windows.Forms.FlatStyle”).System
on btnGetValue MouseClick do
— Get the value auto converted by MAXScript
fValue = upDownCtrl.Value
format “Wrong Value : %n” fValue
— Get the decimal value as a .NET object
dValue = getProperty upDownCtrl #value asDotNetObject:true
— Convert it to single object value then auto converted to float value by MAXScript
fValue = (dotNetClass “System.Decimal”).ToSingle dValue
format “Good Value : %n” fValue
createDialog upDownRolloutTest