Does each elements in theta range from negative infinity to positive infinity ？

[MenSanYan]

Thank you for your excellent implementation of spatial transformer in Tensorflow ! However, I notice the 53-th line of "example.py" as follows:

• "h_fc1 = tf.matmul(tf.zeros([num_batch, 1200 * 1600 * 3]), W_fc1) + b_fc1". What confuses me is the absence of some activation function, such as tf.nn.tanh or tf.nn.sigmoid. Without tanh or sigmoid, the range of theta is certainly not limited. What if a proper activation function is used here ? Could you please provide a good recommendation ? Thank you !